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Niajalili, M. ,
Alitavoli, M. ,
Ansari, R. ,
Haghgoo, M. Amirkabir Journal of Mechanical Engineering (20086032) 56(9)pp. 1227-1248
In the design of structures, it is important that they have the ability to withstand loads. Sandwich panels have received attention due to their lightweight and good absorption. In this research, honeycomb sandwich panels with different core topologies were subjected to simultaneous impulsive loading, and the effect of the amount of loads and the distance between charges on the deformation was evaluated. Due to the high cost of conducting the experimental test, the finite element software has been employed. After validating with the experimental data, the values of 0.5, 1, and 2 kg of selected charge in single and two-point loading at the sandwich panels with square, circular, and octagonal core topologies have been affected and the deformation of sandwich panels has been evaluated. In order to investigate the effect of the distance of charges from each other on the deformation, these are placed at 8, 10, and 12 cm from each other. Then, the amount of deflection of sandwich panels with single-point loading has been compared. According to the investigations, the best topology for absorbing loads is octagonal, so it has less displacement in single and two-point loading in the best case of 14.1 and 12.2 mm, respectively.
Amirkabir Journal of Mechanical Engineering (20086032) 54(2)pp. 391-414
In this study, the free vibrations of functionally graded graphene platelet-reinforced porous nanocomposite plates with various shapes such as rectangular, elliptical, and triangular ones embedded on an elastic foundation are analyzed. To mathematically model the considered plate and elastic foundation, the first-order shear deformation plate theory, and Pasternak model are used, respectively. Three types of graphene nanoplatelet distribution patterns and porous dispersion types through the thickness are considered for the nanocomposite plate. To obtain the effective material properties of the considered nanocomposite, a micromechanical model is employed. Then, the energy functional of considered functionally graded graphene platelet-reinforced porous nanocomposite plates are expressed, and the analytical P-Ritz method is used to solve the vibration problem corresponding to different shapes and boundary conditions, the influences of porosity coefficient, the weight fraction of graphene nanoplatelets, elastic foundation coefficients and also the lengths-to-width and -thickness ratios on the natural frequency are analyzed. It is illustrated that the plate with non-uniform and symmetric of first type porosity distribution pattern and the first type graphene nanoplatelets has a higher natural frequency. Also, by increasing the porosity coefficient, the natural frequency of the plate associated with all patterns of graphene nanoplatelets is reduced.
International Journal of Non-Linear Mechanics (00207462) 174
The purpose of this article is to introduce a novel finite element (FE) approach for investigating the large deformations of three-dimensional (3D) micromorphic hyperelastic continua that have an arbitrary geometry. The 3D micromorphic hyperelasticity formulation is initially presented in a general form. To facilitate the procedure of coding, the vector-matrix counterparts of the aforementioned relations are also provided, which can be conveniently employed in numerical methods. Afterwards, an FE approach is implemented to investigate the large deformations of micromorphic hyperelastic structures under static loading. This is achieved via the user element (UEL) subroutine utilized by the commercial ABAQUS software. Problems with complex domains can be solved using this FE approach. Solving some test problems, including bending of a beam, Cook's membrane under bending load, a cracked spherical shell under external pressure point load and a cracked cylindrical shell under stretching load, demonstrates the fast convergence rate, simple implementation, accuracy and efficiency of the method. In addition, the influences of internal length and scale-transition parameters and geometrical properties on the finite deformation of considered micromorphic hyperelastic structures are evaluated. © 2025 Elsevier Ltd
Dastgir, N. ,
Ansari, R. ,
Hassanzadeh-aghdam, M.K. ,
Sahmani, S. Journal of Vibration Engineering and Technologies (25233920) 13(5)
Purpose: The engineering design of vibrational energy harvesters consisting of piezocomposites is generally a challenging task because of various parameters involved at micro- and macro-scales. This paper aims to comprehensively evaluate vibration energy harvesting from a clamped-free bimorph beam with two layers of particulate piezocomposites. Methods: In this study, a multi-phase computational approach is employed to address the vibration energy harvesting using clamp-free piezocomposite bimorph beams. Two types of piezocomposites are examined, featuring LaRC-SI polyamide as the matrix and BaTiO₃ and PZT-7A as piezoelectric fillers. Using the micromechanical finite element method, electromechanical properties of the representative volume element (RVE) of the piezocomposites are predicted. The parametric studies are conducted to predict and compare output voltage and power, considering factors such as the volume fraction, geometry and type of piezoelectric filler, the series or parallel configuration of the circuit. The mode shapes and natural frequencies under structural weight are also analyzed. Results and Conclusion: The results reveal that increasing the volume fraction of piezoelectric fillers enhances electromechanical properties, leading to higher voltage and power output. Bimorph beams are shown to extract more electrical outputs compared to unimorph beams of the same piezocomposite characteristics. Additionally, a parallel circuit connection of the piezocomposite layers in a bimorph beam enhances the electrical outputs compared to a series connection. It is found that the output voltage and power are significantly increased as the piezoelectric filler aspect ratio increases. The frequency related to the peak voltage and power increases as the fillers’ geometry deviates more from spherical shape. © Springer Nature Singapore Pte Ltd. 2025.
Alidoust, A. ,
Haghgoo, M. ,
Ansari, R. ,
Hassanzadeh-aghdam, M.K. ,
Jang, S. Composites Part A: Applied Science and Manufacturing (1359835X) 191
The piezoresistive sensitivity of aligned carbon nanotube (CNT)-elastomeric nanocomposites is investigated using a mapped conductive network model on finite element simulation. The study aims to investigate the sensor's geometrical parameters, including shape and thickness, to enhance sensitivity under compressive load for applications requiring accurate pressure measurements. Substrates with different thicknesses and shapes are compressed to obtain the most efficient sensor structure including square, rectangular, and circular diaphragms. The developed strain field in the sensor as a result of indenter penetrating or uniform compressive pressure leads to the resistance change. The pertained resistivity to each maximum principal strain state is used directly from the conductive network model. The results disclose a good agreement with experimental data denoting improved sensitivity through bending of thinner sensors with square substrate. Results also reveal a decreased sensitivity for the rectangular indented substrates compared square substrates caused by more concentrated strain distribution during square substrate indentation. © 2025 Elsevier Ltd
Measurement and Control (United Kingdom) (00202940) 58(5)pp. 682-695
This article is aimed to propose a simple yet efficient unified numerical strategy for solving both linear and non-linear optimal control problems. To do so, the general form of quadratic performance index function and nonlinear state equations are considered first. Then, the idea of variational differential quadrature method is used to convert the integral/differential equations to the equivalent algebraic form. Since time is the only independent variable is this research, the finite difference method with an equally-spaced discretization scheme would be a more appropriate technique rather than the differential quadrature approach. So, the implemented numerical solution is called now as the variational finite difference method. The method of Lagrange multipliers is then utilized for minimization purpose and, as a result, the final set of nonlinear algebraic equations are obtained. Finally, the quadratic and triadic forms of non-linearity are considered and an explicit formulation is represented for the residual and Jacobian of the Newton-based iterative solution procedure. To demonstrate the accuracy and efficiency of the proposed approach in the quadratic optimal control area, several benchmark problems involving linear time-invariant, linear time-variant and nonlinear examples are successfully solved and the results are confirmed with those existed in the literature. © The Author(s) 2024.
Journal of Materials Research and Technology (22387854) 34pp. 2909-2918
The performance of polymer-based micro-electronic systems can be evolved by introducing hybrid graphene nanoplatelet (GNP) carbon nanotube (CNT) into the polymer matrix. The electrical conductivity of GNP-CNT polymer nanocomposites is investigated using a conductive network model through electron tunneling considering the subbands effect in an electro-magnetic field. The representative volume element is generated by distributing rode-like CNTs and disk-like GNPs using a Monte Carlo approach. When calculating electrical resistance, the tunneling effect accounts for the electron transfer between each linked pair of nanofillers. The modeling approach consists of the resistance change with the displacement of nanofillers due to strain. When taking into account tunneling behavior in the percolation transition zone, the magnetic field improves the subbands and augments electrical conductivity by transmitting charges. The study reveals that the piezoresistivity of the nanocomposite exhibits a 30% increase at 1.5% strain when the number of subbands is reduced from 20 to 15, or when the aspect ratio is changed from 150 to 100. Additionally, a nanocomposite containing CNTs with a diameter of 20 nm shows a significant increase in conductivity, rising from 10−13 to 10−3 S/m with a 1% increase in volume fraction. © 2025 The Authors
Gholami, R. ,
Ansari, R. ,
Aghdasi p., P. ,
Sahmani, S. Thin-Walled Structures (02638231) 210
In this study, the buckling and postbuckling of embedded sandwich moderately thick rectangular plates with functionally graded graphene platelet-reinforced composite porous core and metallic face sheets are studied. The considered plates are subjected to the uni-axial and bi-axial compressive loadings. Based on the Reddy's third-order shear deformation plate theory and the von Kármán large deflection assumptions, the weak form of discrete nonlinear equilibrium equations of considered sandwich porous plates are derived using the principle of minimum total potential energy. Then, by solving the linear part of achieved equations as an eigenvalue problem, the critical buckling loads and associated modeshapes are obtained. Then, to obtain the equilibrium postbuckling path of sandwich FG‐GPLRC porous rectangular plates with different boundary conditions, the obtained critical bucking loads and modeshapes are considered as the initial guess as well as incrementally applying the applied in-plane compressive load rise. Finally, using the pseudo arc-length technique and modified Newton–Raphson scheme, the set of nonlinear algebraic equations is solved and the equilibrium postbuckling path is obtained. A detailed parametric study is conducted to study the effects of various parameters such as the sandwich core thickness-to-metallic face sheet thickness ratio, porosity coefficient/distribution pattern, GPL weight fraction/distribution pattern and boundary conditions on the critical buckling load and postbuckling strength of FG-GPLRC porous plates. © 2025 Elsevier Ltd
European Physical Journal Plus (21905444) 140(1)
Carbon–nitrogen nanostructures are promising candidates for various technologies due to their unique behavior and potential applications, motivating extensive experimental and theoretical research. N-triphenylene-Graphdiyne (N-TPG) is a carbon–nitrogen nanostructure derived by doping nitrogen atoms into the Graphdiyne family. This work investigates the mechanical properties of N-TPG under tensile stress using molecular dynamics simulations. Initially, the tension distribution and failure locations are discussed, followed by an exploration of N-TPG's behavior under different temperature gradients. The study also introduces defect density in the structure to obtain more realistic properties. Finally, the investigation extends to nanoribbons to explore the effect of size. Young's modulus, ultimate stress, ultimate strain, and tensile toughness are reported under tensile stress. Results show that these properties decrease as the temperature increases in both the X and Y directions and as defect density increases. Young's modulus is about 16% larger in the X direction than in the Y direction at 300K, and the ultimate stress decreases by about 18% and 4% in uniaxial directions with increasing nanosheet dimensions. © The Author(s), under exclusive licence to Società Italiana di Fisica and Springer-Verlag GmbH Germany, part of Springer Nature 2025.
Applied Mathematical Modelling (0307904X) 143
In this paper, a numerical method named as variational differential quadrature-finite element method (VDQ-FEM) is proposed to study the dynamic response of hyperelastic structures with finite deformation in the context of 2D micromorphic theory. Continuum micromorphic hyperelasticity relations are first written in a novel vector-matrix form, which are then discretized using the method of VDQ-FEM. In the next step, the resulting relations are discretized on time domain using Newmark's method in order to study the time response. The presented matricized formulation can be exploited in the coding procedure of numerical techniques. Moreover, VDQ-FEM is capable of addressing problems with irregular domains. Simple implementation, absence of locking problem, fast convergence rate and computational efficiency are the main benefits of proposed numerical approach. Three test problems are solved to show the accuracy and efficiency of developed numerical approach. It is revealed that VDQ-FEM in conjunction with Newmark's method is capable of predicting the dynamic response of micromorphic hyperelastic continua with large deformations in an efficient way. The influences of internal length parameter, density and micro-inertia on the responses of considered micromorphic hyperelastic structures are also analyzed. © 2025 Elsevier Inc.
Functional Composites and Structures (26316331) 7(2)
Highly sensitive thermoresistive composites have great potentials for preventing overheating in electronic devices. Electro-magneto influenced mode numbers have a major effect on the quantum tunneling which has a critical role in electronic applications. A numerical model considering the electrical tunneling effect between carbon nanotubes (CNTs) and graphene nanoplatelets (GNPs) is developed to describe the electrical resistance change induced by mechanical deformation. The multistep percolation model scheme is based on separation distances and surged tunneling proposed to temperature change. The temperature-dependent quantum tunneling and fillers’ movement account for various parameters, such as CNT dispersion, temperature coefficient of resistance and physical properties. Comparisons between results for applied magnetic field suggest an improved conductivity for intensified magnetic field. Moreover, thermoresistivity declares a linear decrease with temperature, in which the highest thermo-resistive sensitivity was measured for highly aligned CNTs reporting a TCR of −0.004 °C. © 2025 The Korean Society for Composite Materials and IOP Publishing Limited. All rights, including for text and data mining, AI training, and similar technologies, are reserved.
Kalashami, E.R. ,
Ansari, R. ,
Hassanzadeh-aghdam, M.K. ,
Sahmani, S. Journal of Thermoplastic Composite Materials (15307980)
In the pursuit of advanced materials with enhanced thermo-mechanical properties, unidirectional short glass fiber (USGF)-reinforced polyethylene composites incorporating alumina nanoparticles can represent a potentially promising development. This study shows the constructive interplay between the multiscale agents, nanofiller/polymer interphase and the overall composite performance, employing the concept of representative volume element (RVE) and the finite element analysis. First, an RVE is created with spherical alumina nanoparticles dispersed randomly within the polyethylene matrix. Next, a different RVE is formed where USGFs are incorporated into the nanoparticle-filled polymer, which serves as the base material. By analyzing the RVEs via the finite element method (FEM), the elastic moduli and coefficients of thermal expansion (CTEs) of the ternary composites are predicted. The validity of the numerical model is assessed by comparison with previous literature, providing an acceptable agreement. The effects of volume fraction and geometry of alumina nanoscale particles and glass microscale fibers on the thermo-elastic constants are investigated. The findings indicate that dispersing alumina nanoparticles into the polyethylene can improve the thermo-elastic properties of the ternary composites. The elastic modulus and CTE in the transverse direction is significantly improved by reducing the diameter of alumina nanoparticles. It is found that nanofiller/polymer interphase region affects mostly the transverse thermo-elastic properties. © The Author(s) 2025
Mahmoudirad m.m., ,
Saghafi h., ,
Khorrami a., ,
Ansari, R. Polymer Composites (02728397)
Laminated composite structures with curved geometries are widely used in various engineering applications due to their lightweight and high-strength properties, but their behavior under low-velocity impact remains a critical area of study. This research experimentally investigates the impact response of curved laminated composites with concave and convex curvatures. Test specimens were designed with three distinct camber heights, and a custom fixture was utilized to conduct impact tests at two initial energy levels, with three repetitions per condition to ensure measurement accuracy. Results indicate that concave specimens exhibit significantly smaller damaged areas compared to convex ones under similar impact energies. Furthermore, increasing camber height leads to a larger damaged area. While delamination and matrix cracking dominate the damage mechanisms across all samples, no fiber breakage is observed in concave specimens. To provide further insights, the study evaluates maximum impact force, maximum displacement, and surface damage using optical imaging of the front and back sides of the specimens. These findings contribute to a deeper understanding of the impact performance of curved composites, informing their design and application in impact-prone environments. Highlights: Experimental analysis of curved composite laminates with low-velocity impact. Optical imaging of front and back surfaces of curvature damage propagation. Identifies distinct failure mechanisms: delamination and matrix cracking. Reveals a correlation between increased camber height and damage zones. © 2025 Society of Plastics Engineers.
Abedi, K. ,
Ansari, R. ,
Hassanzadeh-aghdam, M.K. ,
Sahmani, S. International Journal of Structural Stability and Dynamics (02194554)
While some studies have explored the effective properties of piezoelectric composites under off-axis loading conditions, as well as their performance within energy harvesting (EH) systems, there remains a limited amount of numerical research specifically dedicated to evaluating the performance of piezoelectric vibration energy harvesters (PVEHs) based on poly(vinylidene fluoride) (PVDF)/PZT-7A piezoelectric composites. This research introduces a computational micromechanics approach that utilizes finite element modeling (FEM) to analyze the representative volume element (RVE) of off-axis PZT-7A fiber-reinforced PVDF piezoelectric composites. The electromechanical properties of piezoelectric composites under different fiber volume fractions and off-axis angles are predicted. Furthermore, the efficiency of the PVEH is assessed for different uni/bi-morph cantilever configurations, including both parallel and series arrangements, as well as for exponentially tapered cantilevers. The findings indicate that at a constant off-axis angle (χ) below 45°, increasing the piezoelectric fiber volume fraction (vf) improves the output voltage density. However, once the fiber off-axis angle reaches 45° and exceeds it, a reduction in output voltage density is observed. This phenomenon occurs due to the reorientation of the off-axis fibers, which disrupts the structural symmetry, leading to the development of new components within the piezoelectric, dielectric, and mechanical property matrices. These newly generated components introduce opposing effects on the stress and voltage distribution throughout the PVEH. For a composite with a fiber volume fraction of 60% and an electrical resistance of 100kΩ, the maximum voltage density of 1210.8mV/cm2 is attained at χ = 0°. Significantly, the tapered cantilever design, which is 42% lighter than its uniform counterpart, yields approximately 1.1% greater voltage density. This enhancement can be further increased by up to 19% through the optimized selection of the electrical resistance. These results underscore the significant influence of fiber orientation, volume fraction, and device geometry in optimizing the performance of PVEHs. © 2026 World Scientific Publishing Company.
Moradi, A. ,
Ansari, R. ,
Hassanzadeh-aghdam, M.K. ,
Jamali, J. Computational Materials Science (09270256) 246
Agglomeration of carbon nanotubes (CNTs) refers to their tendency to form clusters, an inevitable phenomenon that markedly influences the performance of composite/nanocomposite materials. Comprehending and managing agglomeration are crucial for tailoring the effective properties of nanocomposites, especially those reinforced with high concentrations of nanofillers. Incorporating this anomaly in numerical simulations can yield significant cost and time savings, while also providing valuable insights into this marvel. This pioneering study explores a promising avenue for a more realistic simulation of CNT-loaded polymer nanocomposites. In the present micromechanics-grounded finite element model, representative volume elements (RVEs) containing CNT agglomerates are ingeniously generated in a three-step stochastic-iterative process. These RVEs are subsequently challenged under commonly encountered engineering scenarios, encompassing elastic, thermoelastic, and viscoelastic aspects. In this case, the precise determination of boundary and loading conditions is accomplished by assessing the constitutive equations associated with each characteristic. Through comparison with available experimental measurements, it has been demonstrated that authoritative prediction of Young's moduli, thermal expansion coefficients, and creep strains necessitates the simulation of building blocks with agglomerated CNTs. © 2024 Elsevier B.V.
Eghbalian, M. ,
Hashemi, M.J. ,
Nikparsa, A. ,
Ansari, R. ,
Sahmani, S. ,
Postek, E. Computational Materials Science (09270256) 258
After the synthetization of graphene, various carbon allotropes with remarkable applications have emerged in the material science. Net Y, closely related to Net C, is a novel carbon allotrope with exceptional properties. This study employs the molecular dynamics simulation to predict key mechanical characters of Net Y subjected to a uniaxial tension, including the failure strain as well as stress, Young's modulus, and strain energy. A detailed tension distribution analysis is provided to explore its mechanical behavior further. The numerical results reveal that the defect density and temperature gradients significantly influence the mechanical performance of Net Y. The nanosheet exhibits over twice the failure stress and 1.5 times the failure strain along with the X direction than the initial failure stress and strain observed along with the Y direction. Also, it is demonstrated that the ultimate failure stress as well as strain along with the Y direction are more significant due to a substantial failure region in the associated stress–strain path. Furthermore, it is observed that the Young's modulus declines consistently allocated to a higher defect density, decreasing by approximately 17 % via increasing the defect density from 0.5 % to 2 % along with the X direction. Moreover, the quantity of strain energy increases with the number of ribbons, reaching 1.58×10-26eV and 3.99×10-26eV along with the X and Y directions, respectively. The study also emphasizes the importance of defect location and structural stability through the tension distribution analysis. © 2025 Elsevier B.V.
Mirsabetnazar a., A. ,
Ansari, R. ,
Ershadi, M.Z. ,
Rouhi h., H. Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science (20412983) 239(9)pp. 3155-3165
Presented herein is a numerical investigation into the free and forced vibrational characteristics of circular plates made of functionally graded graphene origami-enabled auxetic metamaterials (FG-GOEAMs). The material properties of FG-GOEAM are estimated using genetic programing-assisted micromechanical models considering two graphene content distribution patterns. The effects of graphene content, size and folding degree on the material properties are taken into account by the models. The formulation of the paper is in the context of first-order shear deformation plate theory, and the governing equations of motion are achieved utilizing Hamilton’s principle. In the solution approach, the variational differential quadrature (VDQ) method is employed by which the variational statement of problem is directly derived and discretized using matrix differential and integral operators. Selected numerical results are presented to study the effects of graphene origami (GOri) content, folding degree, and distribution pattern on the free and forced vibration responses of FG-GOEAM circular plates with clamped and hinged boundary conditions. © IMechE 2025.
Mirsabetnazar a., A. ,
Ansari, R. ,
Ershadi, M.Z. ,
Sahmani, S. International Journal of Structural Stability and Dynamics (02194554)
Auxetic metamaterials, identified by their negative Poisson's ratio, have attracted the scientific community's attention because of their superior mechanical behavior. In this investigation, the free and forced vibrations of annular plates fabricated from functionally graded (FG) graphene origami-enabled auxetic metamaterials are analyzed using a numerical approach. The micromechanical model is developed using a genetic algorithm to approximate the material properties for two distinct patterns of graphene content distribution and variations in the degree to which graphene origami is folded. The governing equations are attained utilizing Hamilton's principle, incorporating the first-order shear deformation theory of plates. Vibrational responses of annular sector plates are studied for the first time, employing the variational differential quadrature approach directly applied to the variational equations to obtain their discrete form. The proposed model demonstrates excellent agreement with reference solutions, showing a maximum deviation of less than 0.17% in dimensionless frequency values, thereby validating its accuracy and effectiveness. Numerical studies are presented to explore the influence of factors such as graphene content, the degree of graphene origami folding, distribution patterns, and boundary conditions on the free and forced vibration responses of annular sector plates. An inverse relationship between the folding degree and material strength is detected. This discrepancy is attributed to the interaction between graphene content and graphene folding degree. At low graphene content, higher degrees of folding reduce the material's strength. However, when graphene content exceeds 3%, an increase in the degree of folding enhances the material's strength, resulting in decreased lateral deflection. © 2026 World Scientific Publishing Company.
Acta Mechanica (16196937)
In the present article, based on the first-order shear deformation theory (FSDT) and strain gradient theory (SGT), vibrational characteristics of plate-type microstructures made of functionally graded materials (FGMs) with arbitrary shape are numerically investigated. To this end, first, the governing equations are obtained within the frameworks of Mindlin’s SGT and FSDT. The relations are presented in a vector–matrix form so as to use in a numerical approach. Also, the developed SGT-based formulation can be reduced to various simplified theories including MCST and MSGT. Then, the variational differential quadrature (VDQ)-transformed method is applied to the variational statement of problem in the solution procedure. FG microplates under various edge conditions are considered whose free vibration response is analyzed. The developed approach can be used to address the problem for various geometries. Natural frequencies of FG skew, triangular and sector plates are computed, and the effects of thickness-to-length-scale parameter and vibration mode number on the results are studied. It is shown that natural frequencies are considerably decreased by increasing the thickness-to-length-scale parameter ratio. © The Author(s), under exclusive licence to Springer-Verlag GmbH Austria, part of Springer Nature 2025.
Gholami, R. ,
Ansari, R. ,
Sahmani, S. ,
Hassanzadeh-aghdam, M.K. Acta Mechanica (16196937)
In this study, with the aid of a unified micromechanics–time-periodic mathematical model, the geometrically nonlinear free oscillation characteristics of higher-order shear deformable ternary short glass fiber (SGF)/carbon nanotube (CNT) nanocomposite annular sector plates are investigated considering the influences of different material and structural parameters. The effective mechanical properties of the nanocomposite are derived using a finite element-based micromechanical modeling, accounting for the contributions of SGFs and CNTs. The nonlinear governing equations are formulated by utilizing von Kármán nonlinearity relations and solved using a multiphase numerical solving strategy that includes the Galerkin scheme, time-periodic discretization (TPD) approach, pseudo-arc-length continuation method, and modified Newton–Raphson technique. The nonlinear frequency responses are obtained, and the effects of CNT and SGF volume fractions, aspect ratios, dispersion patterns, interphase effects, and CNT morphology are comprehensively analyzed. The results indicate that increasing CNT and SGF volume fractions significantly enhances the nonlinear frequencies of the nanocomposite structure, with higher aspect ratios leading to further improvements. It is also concluded that the alignment of both fillers provides the highest dynamic performance for SGF/CNT nanocomposite annular sector plates. © The Author(s), under exclusive licence to Springer-Verlag GmbH Austria, part of Springer Nature 2025.
Gholami, R. ,
Ansari, R. ,
Hassanzadeh-aghdam, M.K. ,
Sahmani, S. International Journal of Non-Linear Mechanics (00207462) 178
Nonlinear primary resonance behavior of titanium dioxide (TiO2)/graphene nanoplatelet (GNP)/polymer nanocomposite rectangular plates using a geometrically nonlinear higher-order shear deformable plate model is investigated. The material properties of the hybrid nanocomposite, consisting of a polymer matrix reinforced with TiO2 nanoparticles and GNPs are determined through the finite element-based micromechanical modeling. The representative volume elements (RVEs) account for nanofiller geometry, dispersion patterns, and interphase effects to accurately simulate the mechanical properties of the nanocomposite. The nonlinear governing equations of motion are derived using Reddy's third-order shear deformation theory and von Kármán nonlinearity and are discretized via the generalized differential quadrature (GDQ) method. The equations are solved using a multistage numerical procedure combining the Galerkin approach, time periodic discretization (TPD) scheme, and pseudo-arc length continuation technique to obtain nonlinear frequency-response curves under various boundary conditions. The results highlight the pronounced contribution of GNP reinforcement, which significantly enhances the stiffness and nonlinear hardening behavior of the plates, as evidenced by increased linear and nonlinear frequencies and reduced vibration amplitudes. © 2025 Elsevier Ltd
Abedi, K. ,
Ansari, R. ,
Hassanzadeh-aghdam, M.K. ,
Sahmani, S. Mechanics of Advanced Materials and Structures (15210596)
This study investigates the performance enhancement of coupled bending-torsional (BT) vibration energy harvesters (VEHs) by incorporating polyvinylidene fluoride (PVDF)/barium titanate (BaTiO3) piezocomposite layers. A unimorph cantilever beam, subjected to BT vibrations, is analyzed using finite element (FE) modeling to evaluate the impact of BaTiO3 (BTO) fiber orientation and connectivity patterns (0–3 and 1–3) within a PVDF matrix. The influence of fiber orientation on the electromechanical properties of long-fiber piezocomposites (LFPs) and short-fiber piezocomposites (SFPs), as well as their corresponding voltage and power output for BT-piezoelectric vibration energy harvesters (PVEHs), has been numerically investigated. Optimal performance for XZ-piezocomposites with 1–3 connectivity (LFPs) is observed at an off-axis angle of 70˚, yielding average maximum voltages of 7.24 V and power of 26.39 μW across the first two vibration modes. For 0–3 connectivity (SFPs), optimal performance occurs at a 50˚ off-axis angle. Furthermore, increasing the mass ratio enhances the contribution of the second vibration mode, potentially broadening the effective frequency range of the harvester. These findings offer crucial insights for optimizing piezocomposite design in energy harvesting applications, particularly for BT-VEHs. © 2025 Taylor & Francis Group, LLC.
Materials Chemistry and Physics (02540584) 344
Temperature dependence of resistance known as thermoresistivity and sharp enhancement of electrical conductivity known as percolation are unique electrical properties affected by temperature and agglomeration of carbon nanotubes (CNTs), respectively. An investigation of the thermoresistivity of a hybrid agglomerated CNT-graphene nanoplatelet (GNP) polymer strain sensor is conducted, taking into account the tunneling mechanism. Rod-like CNTs and disk-shape GNPs are used to generate the representative volume element for evaluating the piezoresistivity caused by the strain and thermoresistivity induced by temperature. The percolation model predicts the tunneling conductance based on contacts that exist inside conductive channels. It is demonstrated that percolation occurs at a GNP concentration of 1.3 vol% when the GNPs have a lateral size of 1 μm, which represents their largest dimension. The effects of CNT aspect ratio and agglomeration radius, and orientation state on the sensitivity of the piezoresistive strain sensor are analyzed. It is found that the piezoresistivity of the 1 vol% CNT polymer nanocomposite increases by 60 % at 1.5 % strain when the orientation state shifts from randomly oriented to partially aligned or when the aspect ratio changes from 370 to 250. The comparison shows that resistance drops as temperature increases because thermal activation hopping becomes more dominant than the thermal expansion of the matrix. A 1 vol% CNT/polymer nanocomposite with 20 nm diameter CNTs with average length of 1.5 μm experiences a 40 % reduction in resistance over a 110 °C temperature increase. © 2025 Elsevier B.V.
International Journal for Numerical Methods in Engineering (00295981) 126(14)
In this study, the bending, buckling, and free vibration analysis of bi-directional functionally graded porous microbeams with variable thickness are investigated. By utilizing the modified strain gradient theory (MSGT) in conjunction with a sinusoidal shear deformation theory, governing equations are derived using Hamilton's principle within the framework of the non-uniform rational B-spline (NURBS)-based isogeometric analysis (IGA). In addition, the C2-continuity requirement can be easily achieved by increasing the order of the NURBS basis functions. The MLSPs and the material properties of microbeams vary along with both thickness and axial directions based on the rule of mixture scheme. To consider the effects of porosity, two even and uneven distributions are considered. After verifying the accuracy of the presented approach, the influence of the aspect ratio, gradient indices, different boundary conditions, porosity parameters, variable MLSPs, and thickness on the bending, buckling, and free vibration characteristics of microbeams are investigated. © 2025 John Wiley & Sons Ltd.
Gholami, R. ,
Ansari, R. ,
Hassanzadeh-aghdam, M.K. ,
Moradi, A. ,
Sahmani, S. Acta Mechanica (16196937) 236(8)pp. 4699-4725
This study establishes a unified framework to investigate the mechanical properties and geometrically nonlinear free vibration of polymer nanocomposite rectangular plates containing carbon nanotubes (CNTs) and silica nanoparticles (SiO2). A micromechanics-based finite element approach is employed to predict the effective mechanical properties of the hybrid nanocomposite, accounting for factors such as volume fraction, nanofiller geometries, interphase characteristics, and clustering effects. The geometrically nonlinear governing equations are derived using Reddy’s third-order shear deformation plate theory, von Kármán-type nonlinear strain–displacement relations, and Hamilton’s principle. In order to solve the governing equations, a multistep numerical methodology is applied, incorporating the generalized differential quadrature scheme, Galerkin approach, time-periodic differential scheme, pseudo-arc-length continuation algorithm, and modified Newton–Raphson method. A comprehensive assessment of nonlinear frequency response curves is performed with consideration of microstructure-level parameters and boundary condition variations. It is concluded that increasing nanofiller content, leveraging elongated CNTs and fine SiO2, and optimizing nanofiller dispersion patterns significantly enhance both linear and nonlinear frequencies, with fully clamped boundary conditions exhibiting the highest frequencies. When the length (width)-to-thickness ratio of a 1 vol.% CNT/5 vol.% SiO2/polymer nanocomposite plate is 12, the non-dimensional linear frequencies incorporating aligned, randomly oriented, and agglomerated nanofillers are 0.6765, 0.5814, and 0.5237, respectively, under simply supported edges, and 1.187, 1.0196, and 0.9179, respectively, under fully clamped edges. © The Author(s), under exclusive licence to Springer-Verlag GmbH Austria, part of Springer Nature 2025.
Kouhkord, A. ,
Hassani, F. ,
Golshani, A. ,
Ansari, R. Results in Engineering (25901230) 27
Bio-nanoparticle synthesis, essential for advanced drug delivery systems, relies on precise control over particle size, composition, and transport behavior. This study highlights micro-acoustofluidic heat and mass transport modeling as a powerful tool for designing controllable nano-drugs, including nanocarriers for respiratory systems and targeted cancer therapies, where precise control over the physical properties of nanoparticles is critical for successfully accomplishing the intended biological task. The intelligent acousto-microfluidic chamber is designed to overcome the unpredictability of heat and mass transport affecting nanoparticle properties, caused by the complex physics of acoustic streaming phenomena, thereby enabling controlled microfluidic nanoparticle synthesis. The study demonstrates how slight adjustments to the voltage settings and the arrangement of sharp edges can profoundly affect the acoustic streaming, thereby facilitating precise micro reaction phenomena. The optimal models were identified, showcasing varying efficiencies in three defined objective functions mixing, temperature fluctuation, and power consumption of proposed microsystem based on the configuration of sharp edge in the baffle and the actuation voltage. Results indicate that increasing voltage to 15 V significantly elevates the objective function by 131%. Systems with higher alpha exhibit greater temperature variations due to less intense vortices. Configurations with lower alpha and smaller curvature radii promote stable mechanical energy consumption (MEC), mitigating pressure drops. However, increasing alpha alongside higher voltage and curvature radius values leads to a substantial 115% increase in Mechanical Energy Consumption MEC. The outcomes and the intelligent framework presented here serve as a guide for creating AI-integrated micro-electro-mechanical devices, aiming controlled heat and mass transfer for precise nanoparticle synthesis. Precision is crucial in advanced biomedical fields requiring reproducible synthesis of smart nanoparticles responsive to biological and physical stimuli, as well as targeted treatments for tumors and respiratory infections. Integrated microfluidic designs enhance nanoparticle reproducibility and therapeutic effectiveness by precisely controlling heat and mass transfer in microfluidic design process. In these contexts, even minor changes in nanoparticle properties due to slight variations in synthesis conditions can significantly influence therapeutic outcomes, addressing current limitations and promoting successful clinical translation. © 2025 The Authors
Abedi, K. ,
Ansari, R. ,
Haghgoo, M. ,
Hassanzadeh-aghdam, M.K. Applied Physics A: Materials Science and Processing (14320630) 131(5)
This study proposes a comprehensive finite element analysis (FEA) of an architected piezoresistive pressure sensor for micro-electromechanical systems (MEMS), focusing on the effects of different diaphragm cut patterns to enhance sensitivity, linearity, and pressure range. Two designs are introduced: Design-1 with straight cuts and Design-2 with arc-shaped cuts. The investigation evaluates stress distribution, deflection, and output voltage across a Wheatstone bridge circuit under varying applied pressures. In Design-1, straight cuts near the diaphragm edges regulate stress distribution, channeling it across the piezoresistors and achieving an 80% increase in sensitivity compared to the baseline design, with a maximum sensitivity of 0.464 mV/V/kPa and nonlinearity error of 1.03%FSS. Parametric studies identify optimal cut dimensions to maximize sensitivity while ensuring linearity and compliance with small deflection theory. Design-2 incorporates arc-shaped cuts that redistribute stress away from the piezoresistors, extending the pressure range to 7 MPa with nonlinearity error of 0.12% (full-scale span) FSS. The strategic placement and geometries of these cuts enable precise control over stress distribution, allowing for tailored performance enhancements in sensitivity or pressure range to meet specific application requirements. © The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature 2025.
International Journal for Numerical Methods in Engineering (00295981) 126(15)
The aim of this paper is to propose a novel finite element (FE) approach for studying the large deformations of structures with arbitrary geometry in the context of micromorphic hyperelasticity. The 3D micromorphic hyperelasticity is first formulated in a general form based on novel constitutive relations within a Lagrangian framework. In order to implement in the coding procedure, the vector–matrix counterparts of presented relations are also given, which can be used in numerical approaches readily. In the next step, a finite element method is developed to compute large deformations in arbitrary-shaped structures under static loading. The correctness and reliability of the approach are illustrated by solving some test problems. Additionally, the effects of Young's modulus, internal length, and scale-transition parameters on the large deformation behavior of considered micromorphic hyperelastic structures are analyzed. © 2025 John Wiley & Sons Ltd.
Haghighi s., ,
Keramati y., Y. ,
Eghbalian, M. ,
Ansari, R. Fibers and Polymers (12299197) 26(2)pp. 797-812
The effects of the vacancy-type defects in the graphene sheet (GR) and volume fraction (vf) of the GR on Young’s and shear moduli of polylactic acid (PLA) nanocomposite strengthened by the GR (GR/PLA) are investigated. The molecular dynamic (MD) method is implemented and stress–strain evolutions are extracted to explore elastic constants. The simulations demonstrate that adding the defect-free and defective GR in the PLA leads to a vast improvement in tensile and shear moduli. In every vf of the GR, the defective GR/PLA under tensile loadings compared to the defect-free one can endure smaller stress and deformation at the breaking point. Likewise, the bearable stress of the defective GR/PLA subjected to longitudinal shearing is lower than the maximum stress obtained from the defect-free GR/PLA. In any vf of the GR, as the rate of the defects rises, the defective GR/PLA is capable of withstanding a smaller quantity of ultimate stress. However, the variation of the ultimate deformation of defective nanocomposites with the increase of the defect content does not pursue a determined trend, mainly because it is heavily dependent on the distribution pattern and location of defects. Young’s and shear moduli of the GR/PLA experience a downward trend with increasing the degree of the defect. In a desired defect percentage, the stiffness and rigidity of the nanocomposites become larger by choosing a higher GR’s vf. © The Author(s), under exclusive licence to the Korean Fiber Society 2025.
Molecular Simulation (08927022) 51(12)pp. 808-823
Carbon-nitrogen nanostructures hold outstanding promise for advancing technology across numerous fields. Their unique mechanical properties drive substantial experimental and theoretical research, aiming to unlock their full potential for practical applications. N-Graphdiyne (C18N6) is a carbon-nitrogen nanostructure derived by doping nitrogen atoms into Graphdiyne. This study explores the mechanical properties of C18N6 under tensile stress using molecular dynamics simulations. First, an investigation of C18N6's behaviour under different temperature gradients is presented. Next, defect density is applied to the structure to obtain more realistic properties. Finally, the characterisation extends to nanoribbons to explore the effect of size. Young's modulus, first failure stress and strain, and tensile toughness are reported under tensile stress. Results show that Young's modulus is approximately 14% larger in the Y direction than in the X direction at 300 K, and the failure stress decreases by about 37%, with a 0.05 drop in the value of failure strain due to defect density growth. © 2025 Informa UK Limited, trading as Taylor & Francis Group.
Moradi, A. ,
Ansari, R. ,
Hassanzadeh-aghdam, M.K. ,
Sahmani, S. ,
Jang, S. Composites Part B: Engineering (13598368) 305
Barium titanate (BT) nanofillers play a crucial role in polymer nanocomposites due to their remarkable intrinsic properties, which markedly improve the effectiveness of energy conversion. However, the synthesis of BT nanofillers in varied structural profiles, such as nanowires, nanoplatelets, and nanoparticles, along with their dispersion within the polymer matrix, exerts a substantial impact on the overall performance of the nanocomposite. Non-uniform nanofiller dispersion is inherently tied to the development of microstructural defects, including poor compatibility between phases, the formation of voids, and nanofiller agglomeration. This study investigates the influence of BT nanofiller shape and microstructural defects on the effective properties of BT/polydimethylsiloxane (PDMS) piezoelectric nanocomposites. Based on a micromechanics-based finite element framework, representative volume elements (RVEs) of the nanocomposite are generated using a morphology-centric computational simulation, and their Young's moduli, piezoelectric coefficients, and thermal expansion coefficients are subsequently predicted. The results indicate that establishing robust interphase regions, driven by enhanced interfacial compatibility, has a direct impact on elevating system functionality. Additionally, the adverse effects of void defects and nanofiller agglomeration on the effective properties are alleviated through void minimization and agglomerate breakdown. © 2025 Elsevier Ltd
Moradi, A. ,
Ansari, R. ,
Hassanzadeh-aghdam, M.K. ,
Sahmani, S. Composite Structures (02638223) 370
Integrating graphene nanoplatelets (GNPs) and barium titanate nanowires (BTNs) into the polymer enables the formation of a hybrid system, which drives notable advancements: enhancing the interfacial compatibility of nanofillers with the polymer and alleviating defect-related drawbacks; preserving the structural integrity of wire-shaped nanofillers through the stabilizing role of platelet-shaped nanofillers; extending the functional applicability of polymer nanocomposites, particularly in multi-physics domains; etc. This cutting-edge research is directed towards developing a micromechanics-based finite element framework for investigating the coupled-field interactions in GNP/BTN/polydimethylsiloxane (PDMS) piezoelectric nanocomposites. A multi-step stochastic-iterative computational algorithm is employed to generate representative volume elements (RVEs) of this tri-phase system, addressing the key morphological aspects of nanofillers. This algorithm also covers a variety of nanofiller dispersal scenarios, spanning well-dispersed, agglomerated, and hybrid configurations. Parameter-driven analyses underscore the beneficial effects of augmenting the loading of well-dispersed nanofillers, deploying slim GNPs and elongated BTNs, and maintaining proper alignment. The findings reveal that when nanofillers accumulate and form agglomerates, GNP clusters yield a more considerable impact on the degradation of the elastic modulus and thermal expansion coefficient, whereas BTN clusters predominantly influence the piezoelectric coefficient. In addition, the advantageous role of cluster fragmentation is detected universally. © 2025 Elsevier Ltd
Composites Part C: Open Access (26666820) 17
In this article, an efficient numerical approach is developed to study the primary resonant dynamics of rectangular plates with arbitrary boundary conditions made of functionally graded carbon nanotube-reinforced composites (FG-CNTRCs). The problem is formulated in the context of three-dimensional (3D) elasticity theory. Also, a variational approach based on Hamilton's principle together with the variational differential quadrature (VDQ) method is proposed to obtain the discretized governing equations on space domain. Then, the solution procedure on the time domain is completed using the numerical Galerkin method, time periodic discretization method and pseudo arc-length continuation algorithm in order to find the frequency-response curves. It is considered that CNTs are distributed in the thickness direction based on an FG manner considering different patterns. After testing the convergence and validity of developed approach, numerical results are presented to investigate the influences of geometrical properties, CNT's volume fraction and distribution pattern on the nonlinear forced vibration response of plates. © 2025
Gholami, R. ,
Ansari, R. ,
Sahmani, S. ,
Hassanzadeh-aghdam, M.K. Polymer Composites (02728397)
This study numerically examines the nonlinear stability characteristics of fuzzy fiber-reinforced composite (FFRC) rectangular plates. A notable feature of these inhomogeneous materials is the uniform alignment and radial growth of carbon nanotubes (CNTs) of identical lengths on the circumferential surface of carbon fibers. To predict the mechanical properties of FFRCs, a micromechanical modeling approach utilizing a unit cell model is developed. This model incorporates essential microstructural factors, such as the volume fractions of carbon fiber and CNT, the thickness, and the stiffness of the interphase region between the nanotube and the polymer matrix. The mechanical properties obtained from the micromechanical model are then applied to investigate the nonlinear bending and postbuckling behavior of FFRC rectangular plates under various boundary conditions. The variational differential quadrature (VDQ) method is used to derive the weak form of the discretized nonlinear governing equations based on Reddy's third-order shear deformation plate theory (TOSDPT). Additionally, the pseudo-arc-length continuation scheme is employed to trace the bending and postbuckling paths. Comprehensive parametric studies are performed to assess the impact of critical parameters, including CNT volume fraction, carbon fiber content, and interfacial region properties, on the nonlinear bending and postbuckling responses of FFRC rectangular plates. © 2025 Society of Plastics Engineers.
International Journal of Structural Stability and Dynamics (02194554)
This paper investigates the nonlinear vibrational behavior of nanocomposite conical shells reinforced with carbon nanotubes (CNTs) and graphene nanoplatelets (GNPs) within a polymer matrix. A hierarchical micromechanical model is first developed to predict the effective properties of the nanocomposite, considering critical microstructure-level structural phenomena. Initially, using the finite element method and a representative volume element (RVE), the effective properties of the polymer containing CNTs and GNPs are determined. To realistically simulate the nanocomposite's microstructure, CNTs and GNPs are dispersed randomly within the polymer matrix through a comprehensive algorithm. Applying a prescribed displacement to the RVE faces and calculating the resulting reaction forces allows for the extraction of the nanocomposite shell's effective properties. Furthermore, using Hamilton's principle and incorporating von Kármán nonlinear strains, the equations of motion are derived. Through the stress function approach and the Galerkin method, these equations are transformed into an ordinary differential equation. The study examines the effects of nanocomposite properties - such as the volume fractions of GNPs and CNTs, the presence or absence of the interphase region, the agglomeration of nanofillers within the RVE, CNT aspect ratio, and GNP thickness - on the vibration behavior of the conical shell for the first time. Results indicate that increasing the volume fraction of CNTs enhances the natural frequency of the shell, whereas accounting for nanofiller agglomeration reduces the strength and stiffness of the shell. © 2026 World Scientific Publishing Company.
Haghgoo, M. ,
Ansari, R. ,
Hassanzadeh-aghdam, M.K. ,
Sahmani, S. ,
Jang, S. Composites Part A: Applied Science and Manufacturing (1359835X) 199
A numerical simulation based on Monte Carlo conductive network path finding method has been developed to investigate thermomagnetic carbon nanotube (CNT)-graphene nanoplatelet (GNP) polymeric conductive composites. The modeling methodology consists of three sequential phases: the initial estimation of resistivity followed by an assessment of the displacement of nanofillers and the resulting alterations in resistance by variations of intrinsic resistance with temperature. The formation of a continuous conductive path through the touching of the conductive fillers causes the resistivity to decrease 10 orders of magnitude in the percolation region. GNP gives a higher percolation threshold than CNT, with a 60% decrease with doubling its aspect ratio from 200. The material displayed a good response to strain, generating a gauge factor of about 3.6 for 0.5 vol% CNT polymer nanocomposite that reduced by 40% with doubling CNT volume fraction. © 2025 Elsevier Ltd
Nickabadi, S. ,
Askari sayar, M. ,
Alirezaeipour, S. ,
Ansari, R. Mechanics Based Design of Structures and Machines (15397742) 53(6)pp. 4435-4464
Auxetic metamaterials have gained attention due to their unique mechanical properties. Integrating origami structures with cellular structures can significantly enhance their energy absorption capacity under mechanical loads. This study develops a novel auxetic structure by combining a curved origami design with the cross-petal auxetic structure. The structure’s behavior under in-plane compressive loading is analyzed using finite element simulations and validated through experimental testing of 3D-printed specimens. The effects of loading rates (quasi-static, low-, medium-, and high-velocity) and geometrical parameters on energy absorption are examined through parametric studies. Structure grading, based on unit cell wall thickness, is also investigated to enhance performance. Finally, the proposed structure’s energy absorption is compared with two common auxetic metamaterials (reentrant and chiral) under various loading conditions. Results indicate deformation becomes more localized with increased loading velocity, with the proposed design achieving a 70% improvement in energy absorption over non-origami designs and a 16% enhancement through grading. The main contribution of this study is the creation of a hybrid structure combining curved origami and cross-petal auxetic designs, achieving a 70% improvement in energy absorption. The dual plateau stress region and graded design further enhance performance, positioning it as an innovative solution for impact protection and soft robotics. The proposed structure exhibits up to 7.56 times higher specific energy absorption under quasi-static loading compared to reentrant and chiral designs, maintaining superior performance at higher loading velocities. © 2025 Taylor & Francis Group, LLC.
Advanced Materials Interfaces (21967350) 12(12)
In recent years, graphene has emerged as a promising material for flexible wearable sensors due to its exceptional properties, including flexibility, high surface area, excellent conductivity, and remarkable mechanical strength. This review article provides a comprehensive analysis of graphene synthesis techniques, focusing on both traditional methods and advanced laser-based approaches such as laser reduction, laser ablation, and laser-induced graphene. Additionally, various laser fabrication technologies, surface modification strategies are discussed to enhance graphene's physical and chemical properties and heteroatom doping. The article further explores the diverse applications of graphene in wearable sensors, encompassing mechanical sensors, electrophysiological sensors, and gas and humidity sensors. By examining the advancements in fabrication techniques and sensor applications, this study highlights the potential of graphene-based sensors to improve the performance and predictability of wearable devices significantly. © 2025 The Author(s). Advanced Materials Interfaces published by Wiley-VCH GmbH.
Nano-Structures and Nano-Objects (2352507X) 42
Wearable sensors aid in diagnosing various diseases by using chemical, physical, and biological sensing technologies. They also make it possible to continuously and instantly monitor a patient's physiological state. Recently, the demand for sensors that track people's surroundings, fitness and health has increased. In the meantime, the production of flexible and wearable polymer sensors based on biocompatibility, biodegradability, environmentally friendly features and cost-effectiveness has created a significant evolution in the wearable sensor industry. In this review, the most recent researches conducted in the direction of the construction of wearable sensors in different fields including physical, optical, chemical, biochemical and the working mechanism of these sensors have been reviewed. Assisting researchers in selecting the most appropriate selective and sensitive sensor is a key objective of this review. In addition, the applications of these sensors were classified into different categories and discussed in fields such as health care and remote welfare. In general, improving personal health care and monitoring their performance using wearable electrochemical and biosensor technologies have a significant impact on people's daily lives. © 2025 Elsevier B.V.
Thin-Walled Structures (02638231) 211
In this paper, the isogeometric analysis (IGA) is extended to study the size-dependent behavior of bending, buckling and free vibration of in-plane bi-directional functionally graded porous microplates with variable thickness. In order to capture the effect of size, the modified strain gradient elasticity theory, which has three length scale parameters, is used. Regarding to the third-order shear deformation theory, the equations of motions are derived by using the Hamilton's principle and then are discretized based on the IGA approach. The material properties vary continuously through in-plane directions by employing the rule of mixture and the porosity distribution is considered an even type. The C2-continuity requirement can be easily achieved by increasing the order of the non-uniform rational B-spline (NURBS) basis functions larger than two. The influences of the size effect, aspect ratios, boundary conditions, thickness variations, material gradations, and porosity distributions on the deflections, the fundamental natural frequencies, and the buckling load values of the rectangular, circular and elliptical microplates are studied. The obtained results are compared with the previously published studies to show the performance and efficiency of the present research. © 2025 Elsevier Ltd
Thin-Walled Structures (02638231) 215
This paper investigates the nonlinear vibration behavior of axially moving porous functionally graded material (FGM) truncated conical shells supported by an elastic foundation using a stress function method. The governing equations of motion are derived from von Kármán nonlinear strain-displacement relations in conjunction with the Hamilton's principle. The equations are simplified using the Galerkin method and transformed into nonlinear ordinary differential equations, which are solved through the method of multiple scales (MMS). The frequency response is analyzed in the primary, subharmonic, and superharmonic resonance regions. The effects of porosity distribution patterns along the thickness, ceramic-to-metal volume fraction, axial velocity, semi-vertex angle of the conical shell, and geometric parameters are analyzed. Results indicate that increasing axial velocity amplifies hardening behavior and reduces fundamental natural frequency. The semi-vertex angle is found to significantly influence the hardening behavior, while the stiffness of Pasternak and Winkler elastic foundations effectively reduces the peak vibration amplitude. Moreover, Pasternak stiffness exhibits a more pronounced impact on the frequency response than Winkler stiffness. © 2025 Elsevier Ltd
Applied Physics A: Materials Science and Processing (14320630) 131(7)
A conductive network model approach is developed based on induced magneto-electric modes to investigate the thermal energy effect on the quantized resistance of a conductive polymer composite with rolled shape conductors. The concept of modes describes the characterization of energy levels in accordance with the thermal energy when the size of the solid is scaled down to a finite size. The focus relates the parameters of micro-scale phenomenon to macro-scale resistance. Along with the resistance dependence on the proportion of the conductor, the effect of the geometry and tunneling resistance on percolation threshold is simulated. The other part of the modeling approach consists of the resistance change and the ensuing conductor displacement computation. Analyses of piezoresistivity that take tunneling behavior in the percolation transition zone into account show good agreement with experimental data. By increasing the mobility of the charges, the magnetic field increases the electrical conductivity and improves electron transport states affected by the applied field. As a result of scaling the sensitivity to lower values, smaller conductors improve the effectiveness of the conductive network in facilitating charge transport. © The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature 2025.
Thin-Walled Structures (02638231) 212
This investigation presents a comprehensive analysis of the thermomechanical behavior of functionally graded (FG) cylindrical shells subjected to cooling shock employing a novel solution methodology. Utilizing the first-order shear deformation theory, the variational differential quadrature (VDQ) approach is employed to solve the governing equation, which are derived using Hamilton's principle, then complemented by the Newmark integration technique for the time derivatives. The generalized differential quadrature (GDQ) method is employed to solve the one-dimensional transient heat conduction problem. The study systematically investigates the influences of temperature differences, boundary conditions (BCs), power law indices, and thermal load rapidity time on the vibrations and stress distributions across various surfaces of the cylindrical shell. Numerical results demonstrate that significant temperature variations lead to increased vibrational amplitudes and stress concentrations, highlighting the critical role of BCs and material properties in the dynamic behavior of FG cylindrical shells. © 2025
Mirsabetnazar a., A. ,
Ansari, R. ,
Ershadi, M.Z. ,
Rouhi h., H. International Journal of Structural Stability and Dynamics (02194554) 25(16)
Based on the variational differential quadrature (VDQ) method, the bending and buckling characteristics of circular plates made of functionally graded graphene origami-enabled auxetic metamaterials (FG-GOEAMs) are numerically studied in this paper. It is considered that the plate is composed of multiple GOEAM layers with graphene origami (GOri) content that changes in layer-wise patterns. The results from genetic programming-assisted micromechanical models are also employed in order to estimate the material properties. The plate is modeled according to the first-order shear deformation plate theory whose governing equations are obtained using an energy approach in the context of VDQ technique. The governing equations are given in a new vector-matrix form which can be easily utilized in coding process of numerical methods. By means of VDQ matrix differential and integral operators, the governing equations are discretized and solved to calculate the lateral deflection and critical buckling load of plates under various boundary conditions. Selected numerical results are presented to investigate the influences of boundary conditions, GOri content, folding degree and distribution pattern on the buckling and bending behaviors of FG-GOEAM plates. © 2025 World Scientific Publishing Company.
Iranian Polymer Journal (10261265) 33(12)pp. 1677-1688
This study aims to examine how moisture absorption affects the impact behavior of a recently developed sandwich structure designed for use as a water-resistant system in the marine industry. For this purpose, two types of balsa-cored sandwich systems were manufactured, one with conventional glass fiber-epoxy (GE) skins and the other with novel fiber metal laminates (FML) skins. Subsequently, the specimens were exposed to environmental aging through distilled water immersion for 100 days before impact testing. Low-velocity impact behavior was studied using Charpy tests, while high-velocity impact tests were conducted with a light gas gun. The experimental results showed that FML sandwich systems exhibited significantly better impact characteristics compared to GE systems. Before aging, the Charpy impact strength and high-velocity impact absorbed energy of FML systems were 187% and 49% higher than those of GE ones. Another main finding was the impact properties of the FML systems showed a lower decline due to moisture aging compared to the GE systems, for both low- and high-velocity impacts. The reduction of Charpy impact strength and high-velocity impact absorbed energy due to moisture aging in GE systems with sealed edges was about 15%, and 3%, respectively, and for sealed edges FML systems was less than 12% and 1%, respectively. The results also indicated that the high-velocity impact properties of both sandwich systems studied were not significantly affected by moisture aging. In general, the findings suggest that FML skins significantly enhance both the impact resistance and environmental durability in marine balsa-cored sandwich structures. Graphical abstract: (Figure presented.) © Iran Polymer and Petrochemical Institute 2024.
Applied Physics A: Materials Science and Processing (14320630) 130(4)
In this study, we investigate the mechanical properties of armchair phosphorene nanotubes using a combination of density functional theory (DFT) and the finite element method (FEM). Utilizing DFT, we determine the Young’s modulus, flexural rigidity, and Poisson's ratio of armchair phosphorene nanotubes. Subsequently, employing the finite element method based on the analogy of molecular mechanics and structural mechanics, we extract elemental properties for the finite element model. Our analysis reveals that the Young’s modulus of phosphorene nanotubes is intricately linked to the nanotube radius, demonstrating a dependency that converges as the radius increases. Furthermore, an increase in the aspect ratio of phosphorene nanotubes corresponds to an elevation in their Young’s modulus, with a notable exception for small aspect ratios where the impact on elastic properties is minimal. This research significantly advances our understanding of the mechanical behavior of armchair phosphorene nanotubes, offering insights crucial for unlocking their potential in diverse scientific and technological applications. The observed relationships between Young's modulus and nanotube parameters provide valuable considerations for the design and application of nanomaterials, making our findings relevant and influential in both scientific research and industrial endeavors. © The Author(s), under exclusive licence to Springer-Verlag GmbH, DE part of Springer Nature 2024.
Engineering Computations (02644401) 41(1)pp. 68-85
Purpose: In this paper, based on the density functional theory (DFT) and finite element method (FEM), the elastic, buckling and vibrational behaviors of the monolayer bismuthene are studied. Design/methodology/approach: The computed elastic properties based on DFT are used to develop a finite element (FE) model for the monolayer bismuthene in which the Bi-Bi bonds are simulated by beam elements. Furthermore, mass elements are used to model the Bi atoms. The developed FE model is used to compute Young's modulus of monolayer bismuthene. The model is then used to evaluate the buckling force and fundamental natural frequency of the monolayer bismuthene with different geometrical parameters. Findings: Comparing the results of the FEM and DFT, it is shown that the proposed model can predict Young's modulus of the monolayer bismuthene with an acceptable accuracy. It is also shown that the influence of the vertical side length on the fundamental natural frequency of the monolayer bismuthene is not significant. However, vibrational characteristics of the bismuthene are significantly affected by the horizontal side length. Originality/value: DFT and FEM are used to study the elastic, vibrational and buckling properties of the monolayer bismuthene. The developed model can be used to predict Young's modulus of the monolayer bismuthene accurately. Effect of the vertical side length on the fundamental natural frequency is negligible. However, vibrational characteristics are significantly affected by the horizontal side length. © 2023, Emerald Publishing Limited.
Alidoust, A. ,
Haghgoo, M. ,
Ansari, R. ,
Hassanzadeh-aghdam, M.K. ,
Jang, S. Composites Part A: Applied Science and Manufacturing (1359835X) 180
A flexible pressure sensor utilizing carbon nanotubes (CNTs) is investigated employing a finite element methodology to delve into its electro-mechanical behavior. The responsive nature of the three-dimensional representative volume element, containing impenetrable CNT cylinders within an insulating hyperelastic elastomeric cube, is simulated to capture its sensitivity to pressure. Considering applied pressure and updated percolation pathways, a multi-step approach is employed to assess piezoresistivity. Upon adjusting positions of CNTs within the deformed state using the finite element method, novel pathways are identified using the critical distance criterion for percolation paths that contribute to the resistance network. Simulation results demonstrate good agreement with experimental data for resistivity and piezoresistive sensitivity of different CNT elastomeric nanocomposites. The finite element method helps to analyze influences of nanotube volume fraction, geometrical properties, and orientational configurations on the critical distance percolation onset. Lower CNT contents yield more substantial relative resistance changes due to fewer percolating routes. © 2024 Elsevier Ltd
Keramati y., Y. ,
Ansari, R. ,
Haghighi s., ,
Eghbalian, M. Molecular Simulation (08927022) 50(14)pp. 1116-1128
Molecular dynamics (MD) simulations have been performed to determine the reinforcing role of two-dimensional (2D) nanosheets on Young’s and shear moduli of nanosheet-strengthened polylactic acid (PLA). Various volume fractions of nanosheets in addition to different kinds of nanosheets, that is, graphene (GR), silicon carbide nanosheet (SiCNS), and boron-nitride nanosheet (BNNS), are regarded as affecting parameters on the mechanical response. Uniaxial tensile and shear tests are conducted and related stress–strain diagrams are achieved to be used for exploring mechanical properties. It is found that the incorporation of 2D nanosheets into PLA has a noticeable impact on the mechanical behavior of the polymer. In a desired percentage of volume fraction ((Formula presented.)), GR and SiCNS have performed the greatest and least roles in augmenting the mechanical properties of PLA nanocomposites, respectively. Compared to those, the reinforcing effect of the BNNS comes in between. Also, the results show that there is a growing trend in longitudinal and transverse Young’s moduli ((Formula presented.) and (Formula presented.)) and the XY-plane shear modulus ((Formula presented.)) of nanocomposites as the (Formula presented.) of nanosheets increases. © 2024 Informa UK Limited, trading as Taylor & Francis Group.
Synthetic Metals (03796779) 302
Reliable, effective, and environmentally friendly supercapacitors still need development despite the progress made in many nanoscale electrode materials. In this area, composite materials made of organic polymers with high electrical conductivity and metal sulfides with various oxidation states were more attractive. This article describes the design and synthesis of zinc sulfide and polyaniline nanocomposites employing a fast and straightforward electrochemical deposition method and their use as electrode materials for supercapacitors. The structural investigation showed clumped spherical for pAni, hexagonal for pure ZnS, and coexisting hexagonal and spherical phases for ZnS@pAni nanocomposites. The ZnS@pAni nanocomposite demonstrated remarkable electrochemical efficiency and faradaic energy storage capabilities with practical reversibility. Also, an impedance inquiry found that the ZnS@pAni composite has better conductivity and a lower charge transfer resistance than its bulk components. ZnS@pAni//AC was used to create a hybrid asymmetric supercapacitor and displayed a large voltage window up to 2.06 V, 235.24 F g−1 specific capacity, and an ultimate energy density of 144.08 Wh kg−1. Also, when energy density drops to 22 Wh kg−1, substantial power delivery is achieved at 6.3 kW kg−1. Moreover, 88.05% of the capacitance was retained after the device completed 5000 cycles, suggesting good ZnS@pAni//AC asymmetric supercapacitor stability. © 2024 Elsevier B.V.
Alidoust, A. ,
Haghgoo, M. ,
Ansari, R. ,
Jamali, J. ,
Hassanzadeh-aghdam, M.K. Results in Engineering (25901230) 24
Strain sensors have attracted great attentions for practical applications such as human-machine interface. It is challenging to model the electrical behavior of elastomeric strain sensors modified with nanomaterials. This study presents a finite element simulation to explore the piezoresistivity of graphene nanoplatelet (GNP)-filled elastomeric nanocomposites. The percolation network model is employed to determine the critical distance necessary for electrical percolation. The finite element percolation network model uses the Euclidian distance between GNPs distributed inside the representative volume element to calculate the resistivity. The influence of various parameters, including GNP alignment direction, aspect ratio, and volume fraction, on the resistivity changes of the nanocomposite is investigated. Results demonstrate that nearly 20% more tunneling distance is allowed for percolation of nanocomposite with 30% larger aspect ratio GNPs. Findings reveal that as the volume fraction of GNPs increases, the critical distance for the electrical percolation decreases significantly. © 2024
Haghgoo, M. ,
Ansari, R. ,
Hassanzadeh-aghdam, M.K. ,
Jamali, J. Nanotechnology (09574484) 35(32)
In this paper, an analytical model based on the percolation theory has been developed to predict the subbands effect on the effective electrical resistivity of carbon nanotubes (CNT)-based polymer nanocomposites. The CNTs are considered as randomly distributed or aligned channel material in the polymer transmitting electrons through tunneling. The tunneling effect takes into account the electron transmission between each connected pair of CNTs to evaluate electrical resistivity. The modeling approach contains two steps of primary prediction of resistivity and further calculation of CNTs’ displacements and subsequent change of the resistance. A good agreement is found between the analytical model predictions and experimental data when the tunneling behavior was considered in the percolation transition region. The effect of CNT diameter, orientation state, and subbands on the resistivity has been investigated. The results depict that subbands increment is a collateral benefit to the aspect ratio in decreasing the resistivity. The analytical results demonstrate that a random CNT dispersion leads to a decreased piezoresistivity, while an increased strain range depicts a more non-linear behavior. © 2024 IOP Publishing Ltd.
Polymer Bulletin (14362449) 81(5)pp. 4319-4334
In this paper, the creep modulus of polymer/spherical Al2O3 nanoparticle nanocomposites is predicted. An analytical micromechanics model is developed which considers the role of nanoparticle agglomeration and interphase between the nanoparticle and polymer matrix. To show the validity of the micromechanical model, the predictions are compared with the experimental measurements for different nanocomposites. It is found that the creep modulus of the polymer matrix improves by addition of a low content of Al2O3 nanoparticles. However, the nanoparticle agglomeration which may be generated at high content, decreases the creep modulus of nanocomposites. A uniform dispersion of nanoparticles into the polymer matrix is needed to have highest mechanical properties of polymer/Al2O3 nanocomposites. Formation of interphase with higher mechanical properties than the polymer matrix can enhance the nanocomposite creep modulus. By the use of micromechanical model, the effect of elastic modulus and thickness of the interphase between the polymer and nanoparticle on the nanocomposite creep modulus is investigated. © The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature 2023.
Mirnezhad m., M. ,
Ansari, R. ,
Falahatgar s.r., S.R. ,
Aghdasi p., P. Scientific Reports (20452322) 14(1)
In this paper, the quantum effects of fine scaling on the buckling behavior of carbon nanotubes (CNTs) under axial loading are investigated. Molecular mechanics and quantum mechanics are respectively utilized to study the buckling behavior and to obtain the molecular mechanics coefficients of fine-scale nanotubes. The results of buckling behavior of CNTs with different chiralities with finite and infinite dimensions are given, and a comparison study is presented on them. The differences between finite and infinite nanotubes reflect the quantum effects of fine scaling on the buckling behavior. In addition, the results show that the dimensional changes highly affect the mechanical properties and the buckling behavior of CNTs to certain dimensions. Moreover, dimensional changes have a significant effect on the critical buckling strain. Beside, in addition to the structure dimensions, the arrangement of structural and boundary atoms have a major influence on the buckling behavior. © The Author(s) 2024.
Saberi, M. ,
Moradi, A. ,
Ansari, R. ,
Hassanzadeh-aghdam, M.K. ,
Jamali, J. Alexandria Engineering Journal (11100168) 108pp. 344-353
There exists a pressing need for polymeric nanocomposites exhibiting enhanced electrical properties when subjected to external electric fields. Via the development of an efficient model based on the physical-analytical relations, the electrical conductivity and percolation threshold of ternary nanocomposites enriched with the synergy of carbon nanotubes (CNTs) and graphene nanoplatelets (GNPs) are investigated. In so doing, the electrical conductivity of carbon nano-additives is first computed using a discretizer scheme, and subsequently, by incorporating the basic electrical conduction mechanisms and employing the average polarization theory, insights into the overall electrical behavior of CNT/GNP/polymer networks are elucidated. The formulation of the extended framework is in the form of case assessments covering effects of volume fraction and geometry of carbonaceous nanofillers, contribution of the interphase region, which serves as an electron hopping duct, tunneling distance, and electrical potential barrier height. In connection with validation, satisfactory alignment between the predicted outcomes and experimental results substantiates the efficacy of the proposed approach for both binary and ternary nanocomposites. Moreover, parametric studies reveal the remarkable sensitivity of electrical properties of nanocomposites to the aforementioned factors. These findings are valuable and enlightening for the design and manufacturing of highly conductive systems, resulting in time and financial savings. © 2024 The Authors
Mirsabetnazar a., A. ,
Ansari, R. ,
Zargar ershadi m., M. ,
Rouhi h., H. Materials Today Communications (23524928) 41
The behaviors of annular sector plates made of functionally graded graphene origami-enabled auxetic metamaterials (FG-GOEAMs) under the action of buckling and bending loads are investigated herein using a numerical approach. Multiple GOEAM layers with graphene origami (GOri) content are considered for the plate which changes in layer-wise patterns. Moreover, the material properties of the plate are calculated using novel genetic programming-assisted micromechanical models. In order to derive the governing equations, the Mindlin plate theory in conjunction with Hamilton's principle is utilized within the framework of the variational differential quadrature (VDQ) method. The vector-matrix representation of the presented formulation can be beneficial from the viewpoint of implementing numerical approaches. The governing equations are then discretized and solved based on VDQ matrix differential and integral operators so as to obtain the critical buckling load and maximum lateral deflection of plates with different edge conditions. The effects of GOri content, folding degree and distribution pattern on the results are studied. It is revealed that increasing the GOri content leads to the negative Poisson's ratio (NPR) effect which respectively reduces and increases the lateral deflection and the critical buckling load. © 2024
Mirsabetnazar a., A. ,
Ansari, R. ,
Zargar ershadi m., M. ,
Rouhi h., H. Journal Of The Brazilian Society Of Mechanical Sciences And Engineering (16785878) 46(12)
In this paper, an efficient numerical approach is developed to address the linear bending, free vibration and buckling problems of beams made of functionally graded graphene origami-enabled auxetic metamaterials (FG-GOEAMs). It is considered that the beam is composed of multiple GOEAM layers with graphene origami (GOri) content which changes in layer-wise patterns. The material properties of the beam are also computed based on the genetic programming-assisted micromechanical models. The governing equations are derived within the framework of Timoshenko beam theory using Hamilton’s principle and the variational differential quadrature (VDQ) method. The formulation is presented in a novel vector–matrix form, and the VDQ technique is directly applied to the weak form of equations, so that the derivation process of the strong form of the equations is bypassed. The governing equations are solved after discretizing via VDQ matrix operators. Parametric studies are conducted to show the effects of GOri content, folding degree and distribution pattern on the critical buckling load, fundamental frequency and maximum lateral deflection of FG-GOEAM beams subject to various end conditions. © The Author(s), under exclusive licence to The Brazilian Society of Mechanical Sciences and Engineering 2024.
Haghgoo, M. ,
Alidoust, A. ,
Ansari, R. ,
Jamali, J. ,
Hassanzadeh-aghdam, M.K. Composites Part A: Applied Science and Manufacturing (1359835X) 187
Resistivity and piezoresistive sensitivity of Carbon Black (CB) elastomeric nanocomposites are studied using a finite element method with a conductive network model. CB spheres are placed into Representative Volume Elements (RVEs) in random positions to perform simulations and obtain the strained state and new position of particles. Numerical results are implemented into a breadth-first search algorithm tailored to find percolation pathways from one end of the RVE to another based on the shortest distance between CBs in the strained regime. Percolation pathways are used by the conductive network model to determine the critical distance for resistivity. Resistivity diminishes as the critical distance increases attributed to a greater number of electrons penetrating the barriers. Critical distance at which tunneling can occur expands with an increase in barrier potential. Smaller CBs that can more efficiently occupy the gaps lead to a reduction in the critical distance range necessary for percolation to happen. © 2024 Elsevier Ltd
Bulletin of Materials Science (02504707) 47(2)
In this study, semi-infinite two-section nanotubes of different radii are used as nanocontainers to encapsulate spherical fullerenes. In particular, the encapsulation behaviours of C60 and B36N36 fullerenes inside carbon nanotubes (CNTs) and boron nitride nanotubes (BNNTs) are investigated. In order to determine the van der Waals (vdW) interactions between fullerenes and two-section nanotubes, the continuum approximation along with the classical 6-12 Lennard–Jones (LJ) potential function is employed. The proposed continuum model provides explicit analytical expressions for the evaluations of total potential energy and interaction force. Moreover, the suction energy, a measure of the total increase in the kinetic energy experienced by the core, is derived as a function of geometrical parameters and materials of fullerene and nanotube. For C60-CNT, C60-BNNT, B36N36-CNT and B36N36-BNNT mechanisms, the distributions of vdW interactions as well as the nature of suction energy are studied in detail. It is demonstrated that the weakest and strongest interactions are related to C60-CNT and B36N36-BNNT mechanisms. In addition, the interaction of B36N36-CNT mechanism is found to be stronger than that of C60-BNNT one. It is further found that the length of the first section of the nanotube has a negligible effect on the vdW interactions and suction energy. The results of this study also suggest that for a given type of fullerene, the suction radius of CNTs is smaller than that of BNNTs. By contrast, the optimal radius that gives rise to maximum suction energy is unique for all considered mechanisms. The present theoretical study presents deep insights into the basic concepts of encapsulation behaviour and it could be useful to guide the design of novel nanodevices where the nanocapsule may be utilized as a drug container. © Indian Academy of Sciences 2024.
Saberi, M. ,
Moradi, A. ,
Ansari, R. ,
Hassanzadeh-aghdam, M.K. ,
Jamali, J. Composites Part A: Applied Science and Manufacturing (1359835X) 185
Inter-cluster bridging of carbon nanotubes (CNTs) and carbon black (CB) nanoparticles conjoins inactive branches of carbonaceous nanofillers within the matrix and reduces the electron tunneling distance. This mechanism moderately overcomes quantum tunneling and provides percolative polymer networks exhibiting favorable electrical responses. This study focuses on devising an analytical procedure to scrutinize the electrical conductivity and percolation threshold of CNT/CB/polymer nanocomposites. To involve the physics of electrical processes, the modeling approach considers cylindrical CNTs and spherical CB nanoparticles surrounded by a continuum interphase, which serves as an electron hopping duct. This model is extended in a bottom-up micromechanics generalization to a level where it is capable of predicting the effects of a wide range of microstructural properties. The comparison of predictions with those obtained via experimental examinations, while affirming the infrastructure for investigating the electrical behavior of binary systems, convincingly captures the electrical conductivity/percolation threshold of ternary nanocomposites containing CNT/CB nanofillers. © 2024 Elsevier Ltd
Journal of Molecular Graphics and Modelling (10933263) 129
In this paper, the finite element method is utilized to evaluate the behavior of the armchair phosphorene nanotubes under the compressive loading. The energy equations of the molecular and structural mechanics are used to obtain the elemental properties. The critical compressive forces of various armchair phosphorene nanotubes are computed with clamped-clamped and clamped-free boundary conditions. Results show that the stability of armchair phosphorene nanotubes increases with increasing nanotube aspect ratio, particularly under clamped-clamped boundary conditions. Finally, the buckling mode shapes of armchair phosphorene nanotubes under different boundary conditions are compared. Our work offers valuable insights into how these nanotubes respond to mechanical stress, helps determine elemental properties, and investigates the effects of nanotube geometry and different boundary conditions on their stability. This knowledge has broad applications in fields like nanotechnology, materials science, and nanomechanics, advancing the understanding of nanoscale materials and their potential for various practical uses. © 2024 Elsevier Inc.
Materials Science in Semiconductor Processing (13698001) 174
In the current study, the density functional theory is utilized to investigate the elastic, plastic and electronic properties of the 2×2 and 3×3 pristine and transition metal (TM) doped germanene. Different atoms, including V, Co, Fe, Mn, Cr, Ti, Ni and Sc are selected for this purpose. It is shown that doping of the transition metal atoms would result in the reduction of the Young's and bulk moduli of the germanene. In addition, the isotropic behavior of these nanosheets were shown by comparing the Young's moduli of both pristine and doped structures in armchair and zigzag directions. Furthermore, the plastic behavior of these structures were investigated by increasing the applied loading. It was seen that except for the 2×2 Co-doped monolayer, the yield strain of both 2×2 and 3×3 nanosheets were reduced under uniaxial and biaxial loading. In 2×2 doped nanosheets under uniaxial loading, the highest reduction occurs for Ti-doped germanene, and in 3×3 cases, the highest reduction happens for Co, Ni, Fe and Sc-doped germanene. Electron localization function revealed the ionic nature of the boding between TM atoms and germanium while the density of state indicated that doping of transition metals would change the semi-metallic behavior of germanene to metallic except for Ti-doped structure. The findings provide valuable information for potential applications in nanotechnology, guiding the development of new materials with specific characteristics based on the identified impacts of different transition metals. © 2024 Elsevier Ltd
Rahnama, E.K. ,
Ansari, R. ,
Hassanzadeh-aghdam, M.K. Proceedings of the Institution of Mechanical Engineers, Part L: Journal of Materials: Design and Applications (20413076) 238(6)pp. 1082-1098
In this article, the effect of graphene nanoadditives on the fatigue limit of unidirectional glass fiber-reinforced polymer (GFRP) composites has been investigated. A micromechanical model based on the crack growth has been used to analyze the fatigue limit response of unidirectional GFRP hybrid composite containing nanoadditives. The influence of different percentages of graphene nanosheets (GNS) and different types of nanofiller dispersion has been investigated by the micromechanical model. The fatigue limit of unidirectional GFRP hybrid composites has been plotted in terms of glass fiber volume fraction, interfacial friction shear stress, interfacial fracture energy and reference length. The fatigue limit of unidirectional composites can be improved by addition of GNS into the polymer matrix of such composite systems. The obtained results on the GNS dispersion type demonstrate that the uniform dispersion of GNS into the polymer matrix increases the fatigue limit of unidirectional GFRP hybrid composites. As the agglomeration density of GNS is low, the fatigue limit of GFRP hybrid composites will be improved more than when the density of agglomeration is high. © IMechE 2023.
Haghgoo, M. ,
Ansari, R. ,
Hassanzadeh-aghdam, M.K. ,
Jamali, J. Sensors and Actuators A: Physical (09244247) 373
The effective electrical resistivity of carbon nanotubes (CNT)-based polymer nanocomposites is studied using an analytical model based on the percolation theory. The CNTs are considered as rod-like conductors that are aligned or randomly dispersed in the polymer to transport electrons by tunneling. When assessing non-zero temperature electrical resistivity, the tunneling effect considers the thermally energized electron transmission that occurs between each coupled pair of CNTs by the electrical transport model. The modeling technique consists of three steps: identifying the percolating network from the primary formation of CNTs, initial prediction of resistivity by equivalent resistor network, computation of the displacements of CNTs for the resistance change. Taking into consideration the behavior of tunneling in the percolation transition zone, a good agreement is obtained between the model results and experimental data. The verified code is used to investigate the sensitivity for different orientation states, aspect ratios and mode numbers. The results reveal lower sensitivity for higher mode numbers as collateral with the influence of increasing randomness. © 2024 Elsevier B.V.
Haghgoo, M. ,
Alidoust, A. ,
Ansari, R. ,
Hassanzadeh-aghdam, M.K. Smart Materials and Structures (09641726) 33(5)
A finite element (FE)-percolation model approach is developed to predict the strain-sensitive response of the three-dimensional (3D) representative volume element (RVE) of carbon nanotube (CNT)-elastomeric nanocomposite. In the simulation model, CNTs are modeled as solid, impenetrable cylinders inside a cubic insulating matrix. FE simulation is performed to evaluate the structural response of the RVE under applied strain. The FE model updates the locations of the CNTs in the deformed RVE. The paths are found using a suitable 3D resistance network associated with different percolation paths involved in the critical distance criterion. The percolation model utilizes the paths found to identify the electrical circuit for predicting tunneling conductivity. The simulating algorithm is used to study the influence of tunneling barrier height, nanotube volume fraction, and geometrical aspects. The lowest critical distance criterion is achieved for higher volume fractions and the most heightened sensitivity is obtained for lower CNT aspect ratios. © 2024 IOP Publishing Ltd.
Moradi, A. ,
Ansari, R. ,
Hassanzadeh-aghdam, M.K. ,
Jamali, J. Mechanics of Advanced Materials and Structures (15210596) 31(24)pp. 6109-6125
A micromechanical model implemented with the finite element method (FEM) using the representative volume element (RVE) approach is developed to investigate the creep compliance behavior of carbon nanotube (CNT)-polymer nanocomposites. Effects of the CNT waviness, orientation, volume fraction and aspect ratio on the creep compliance of the nanocomposite are examined. Contribution of the interphase region formed due to the interaction between CNTs and matrix to the nanocomposite creep behavior is considered. The nanocomposite creep behavior is affiliate on the waviness and orientation of CNTs. Increasing the volume fraction and length of CNT and interphase thickness improves the nanocomposite creep performance. © 2023 Taylor & Francis Group, LLC.
Moradi, A. ,
Ansari, R. ,
Hassanzadeh-aghdam, M.K. ,
Jamali, J. Mechanics of Advanced Materials and Structures (15210596) 31(27)pp. 9117-9129
Effects of incorporating carbon nanotubes (CNTs) and short carbon fibers (SCFs) into the polyvinyl chloride (PVC) foam core on the flexural behavior of sandwich beams are investigated. Upper and lower skins are made of laminated composites and an initial debonded interface among the upper skin and core is considered. The mechanical properties of the hybrid CNT/SCF/PVC core are determined employing micromechanical models. To inspect the flexural behavior of sandwich beams at macro-scale, end notched shear (ENS) test is simulated using the finite element method (FEM). The results indicate an increase in flexural stiffness in the presence of CNT and SCF. © 2023 Taylor & Francis Group, LLC.
Applied Physics A: Materials Science and Processing (14320630) 130(4)
First principle calculations are used here to obtain the mechanical properties of the monolayer zigzag phosphorene nanosheet. These properties are used to compute some force constants. A finite element model is proposed to investigate the mechanical properties of the zigzag phosphorene nanosheets which is formed by some beam elements. The properties of the beam elements are functions of the mentioned forced constants. The proposed finite element model is used to study the mechanical properties of the monolayer zigzag phosphorene nanosheet under the tensile and compressive loadings. It is shown that the proposed finite element model can predict the mechanical properties of the zigzag phosphorene nanosheet with good accuracy. The multiscale analysis in this study leverages finite element analysis as a distinctive approach, complementing the nanoscale capabilities of density functional theory and molecular dynamics by overcoming limitations faced by these two methods in representing complex scenarios. Furthermore, finite element analysis demonstrates computational efficiency for larger structures, making it suitable for systems where atomistic simulations may be impractical. © The Author(s), under exclusive licence to Springer-Verlag GmbH, DE part of Springer Nature 2024.
Ansari, R. ,
Zargar ershadi m., M. ,
Laskoukalayeh, H.A. ,
Oskouie, M.F. ,
Rouhi h., H. International Journal of Structural Stability and Dynamics (02194554) 24(9)
The nonlinear vibration response of rectangular plates made of functionally graded porous materials (FGPs) induced by hygrothermal loading is investigated in this article using a numerical approach. The effect of elastic foundation on the vibrations is taken into account according to the Winkler-Pasternak model. Hygroscopic stresses produced due to nonlinear rise in moisture concentration are also considered. The temperature-dependent material properties of plate are computed based on the modified Voigt's rule of mixture and Touloukian experiments for even and uneven distribution patterns of porosity. Within the framework of the first-order shear deformation plate theory and von-Kármán nonlinearity, Hamilton's principle is utilized in order to derive the equations of motions. To achieve the temporal evolution of maximum lateral deflection of hygrothermally-induced plates, the generalized differential quadrature (GDQ) and Newmark integration methods are employed. Selected numerical results are presented to study the influences of temperature distribution, porosity volume fraction, moisture concentration, geometrical parameters, elastic foundation parameters and FG index on the geometrically nonlinear vibrations of FG porous plates with various boundary conditions. © 2024 World Scientific Publishing Company.
Surface and Interface Analysis (01422421) 56(9)pp. 616-627
Current study presents a novel hybrid approach combining finite element modeling and density functional theory calculations to investigate the mechanical properties of monolayer puckered arsenene. The multiscale analysis in this study leverages finite element analysis as a distinctive approach, complementing the nano-scale capabilities of density functional theory and molecular dynamics by overcoming limitations faced by these two methods in representing complex scenarios. Furthermore, finite element analysis demonstrates computational efficiency for larger structures, making it suitable for systems where atomistic simulations may be impractical. This hybrid methodology offers a unique framework for accurately predicting key properties, including elastic modulus and buckling force, by synergistically integrating the strengths of both computational techniques. In addition to demonstrating the effectiveness of our approach in accurately capturing material behavior, our findings shed light on fundamental aspects of nanoscale mechanics, with implications for various applications in nanotechnology, materials science, and structural engineering. By providing a deeper understanding of the mechanical response of 2D materials, our research contributes to advancing the field of nanoscale materials engineering and informs the design of innovative nanostructures with tailored mechanical properties. © 2024 John Wiley & Sons Ltd.
Ansari, R. ,
Zargar ershadi m., M. ,
Akbardoost laskoukalayeh h., ,
Rouhi h., H. Mechanics Based Design of Structures and Machines (15397742) 52(9)pp. 6841-6857
In the present research, the large-amplitude vibration behavior of rectangular plates subjected to cooling shock is investigated based on a numerical solution approach. It is considered that the plates are made of functionally graded materials as a mixture of stainless steel and low-carbon steel. The thermoelastic properties are also considered temperature-dependent which are estimated based on available experimental data. According to the Mindlin plate theory, the nonlinear governing equations of motion together with corresponding boundary conditions are derived. The temperature profile is also obtained based on a one-dimensional Fourier-type transient heat conduction equation. Moreover, two time-dependent thermal loading scenarios for cooling shock on the plate’s top face are considered. To solve the problem numerically, the well-known generalized differential quadrature technique is used for discretization considering the Chebyshev–Gauss–Lobatto grid. In addition, the governing equations are traced in time by Newmark’s time integration scheme. After showing the validity of developed approach, a parametric study is presented to investigate the stress changes along the thickness and the effects of thermal load rapidity time, geometry, magnitude of thermal load, and material properties on the nonlinear vibrations of plates with various boundary conditions subjected to sudden decrease of temperature. It is concluded that the thermal load rapidity time has a significant role in the vibrational behavior and the stress distribution of the plate. © 2023 Taylor & Francis Group, LLC.
Archive of Applied Mechanics (14320681) 94(4)pp. 801-818
In this paper, the nonlinear large-amplitude vibrations of shallow arch structures made of functionally graded materials (FGMs) under cooling shock have been investigated. It is considered that the FG shallow arch is made of low carbon steel AISI1020 and stainless steel (SUS304), whose material properties change in the thickness direction. Using the kinematic assumptions that are modeled based on the first-order shear deformation theory (FSDT) and the von Kármán’s geometrical nonlinearity; along with the aid of Hamilton’s principle, the shallow arch motion equations are obtained. The material properties vary in the direction of arch’s thickness due to the temperature changes and material distribution. Based on the Voigt rule of mixture and power law distribution, the dependence of material properties on temperature and material distribution is defined. Assuming uncoupled theory of thermoelasticity, first, the one-dimensional heat conduction equation is solved along the thickness of the arch in order to obtain the temperature distribution. Afterward, the equations of motion are solved. For the numerical solution of the heat conduction equation and the nonlinear equations of motion, the iterative hybrid method of generalized differential quadrature and the Newmark time integration scheme has been used in an iterative Newton–Raphson loop. After validating the present formulation, a parametric scrutiny is conducted regarding the influence of various parameters, namely, thermal load rapidity time, FG-index, dimensional parameters on the mid-plane non-dimensional lateral deflection of the arch as well as the changes in stress and material properties. © The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature 2024.
Mechanics of Advanced Materials and Structures (15210596) 31(8)pp. 1655-1665
The aim of current investigation is to study the dynamic behavior of shells made of unsymmetric laminated composites. Based on the higher-order shell model with twelve parameters, a shell element with four nodes is designed and equipped with the ANS method to circumvent the transverse shear locking. Next, by using the Hamilton’s principle, the mass and the stiffness matrices as well as the load vector are extracted. Additionally, the standard Newmark approach for the numerical time integration is employed. Some problems involving plates and cylindrical and spherical shells are solved to verify the performance of the proposed finite element formulation. © 2023 Taylor & Francis Group, LLC.
Engineering with Computers (14355663) 40(3)pp. 1431-1450
The concentration of the current contribution is on the geometrically nonlinear analysis of laminated composite shells employing the finite element method. For this purpose, the use is made of a higher-order shell model with extensible directors possessing twelve parameters, then the exact Green–Lagrange strains and the three-dimensional second Piola–Kirchhoff stress tensor are extracted based on the base vectors of the shell mid-surface. The principle of virtual work is adopted to derive the weak form of governing equations. A computationally efficient four-node shell element is designed and to remedy the locking problems involving transverse shear, membrane and curvature–thickness ones, the ANS (assumed natural strain) approach and the assumed strain scheme are used. Finally, standard benchmarks are solved for isotropic materials allowing geometric nonlinearity to examine the performance of the proposed shell element and then results of thin and thick layered composite structures are presented. © The Author(s), under exclusive licence to Springer-Verlag London Ltd., part of Springer Nature 2023.
Ansari, R. ,
Ershadi, M.Z. ,
Mirsabetnazar a., A. ,
Oskouie, M.F. Journal Of The Brazilian Society Of Mechanical Sciences And Engineering (16785878) 46(9)
In this paper, the nonlinear large amplitude vibrations of functionally graded material porous annular sector plates have been investigated. The effects of considering nonlinearity in scrutinizing the large amplitude thermally induced vibrations of the annular sector plates have been studied. Additionally, in this work, the effects of moisture distribution and the presence of material porosity are taken into account. Material and temperature distribution in the thickness direction of the plate cause changes in the hygro-thermo-mechanical material properties in the corresponding direction. To define the dependence of material properties on position and temperature, the power law distribution and the Touloukian formula are employed, respectively. Next, according to the classical theory of thermoelasticity, the one-dimensional heat conduction equation along the thickness direction of the plate is solved and the temperature profile is obtained. Afterward, knowing the temperature distribution, the nonlinear equations of motion, which are derived employing Hamilton’s principle, are solved for each time step. To numerically solve the equations, first, using the generalized differential quadrature method (GDQM), the spatial derivatives are discretized and a differential equation with only the time derivatives is achieved, then the time-dependent differential equation is solved utilizing the Newmark implicit time integration method. Finally, a parametric numerical analysis is conducted to investigate the effects of various parameters on the vibrational behavior of the plate. © The Author(s), under exclusive licence to The Brazilian Society of Mechanical Sciences and Engineering 2024.
Mechanics Based Design of Structures and Machines (15397742) 52(2)pp. 1042-1059
In this work, the nonlinear vibrations of functionally graded (FG) porous circular plates under hygro-thermal loading is studied utilizing a numerical approach. Hygroscopic stresses generated due to the nonlinear rise in moisture concentration, even and uneven porosity distributions, and temperature dependency of material properties are all taken into account. Modified Voigt’s rule of mixture is applied to obtain the hygro-thermo-mechanical properties of the FG circular plate. All material properties are assumed to be temperature-dependent using the Touloukian formula. In order to obtain the equations of motion, the first-order shear deformation theory, von-Kármán geometrical non-linearity assumption, and hygro-thermal strains are considered concurrently. After deriving the equations of motion using Hamilton’s principle, the differential quadrature method and the Newmark-beta time integration scheme are employed in conjunction with an iterative approach to solve the set of nonlinear governing differential equations of motion. The effects of various parameters including temperature distribution, plate’s thickness, porosity volume fraction, moisture concentration, and FG index are studied on plate’s maximum non-dimensional lateral deflection. © 2022 Taylor & Francis Group, LLC.
Moradi, A. ,
Ansari, R. ,
Hassanzadeh-aghdam, M.K. ,
Jamali, J. Journal of Composite Materials (00219983) 58(9)pp. 1123-1136
The optimal performance of composites enriched with hollow spheres has been reported in contemporary literature, whereas their thermal properties have received less attention. In this regard, a finite element method (FEM)-based micromechanical model has been developed systematically to investigate the role of intra-matrix embedding of hollow spheres on the thermal conductivity and coefficient of thermal expansion (CTE) of unidirectional fiber-reinforced hybrid composites. In so doing, the concept of representative volume element (RVE) considers microstructures comprising an epoxy matrix, E-glass fiber, and E-glass hollow spheres, assuming perfect bonding (ideal interface) between the components and modified approximate periodic boundary conditions. By computing the longitudinal and transverse temperature gradients generated due to the application of uniform heat flux as well as the geometrical variation in RVE owing to temperature enhancement, thermal conductivity and CTE have been respectively determined. Comprehensive evaluations have been conducted to examine the effects of microstructural-level features, including fiber volume content and orientation, plus volume content and thickness of hollow spheres, on the effective thermal conductivity and CTE of pseudo-porous ternary E-glass/epoxy composites. © The Author(s) 2024.
Nickabadi, S. ,
Sayar, M.A. ,
Alirezaeipour, S. ,
Ansari, R. Journal of Sandwich Structures and Materials (15307972) 26(7)pp. 1129-1164
Auxetic metamaterials, characterized by their negative Poisson’s ratio, offer promising prospects for utilization in absorbing energy during quasi-static compressive loading as well as in applications requiring impact energy absorption. The optimization of auxetic structures’ geometrical parameters can improve their performance. This research aims to optimize the design of an auxetic structure for maximum specific energy absorption and investigate its behavior under quasi-static compressive and high-velocity impact loading. The geometrical parameters of the cross-petal auxetic structure are optimized using genetic algorithm and a neural network surrogate model. The behavior of the optimized auxetic structure is examined in quasi-static compressive loading and compared with that of the basic auxetic structure using finite element simulations. The optimized auxetic structure is then evaluated in high-velocity impact loading as the core of a sandwich panel, with two plates placed in the front and rear. Simulations of projectile impacts at velocities ranging from 100 to 250 m/s reveal the sandwich panel’s behavior. Results indicate a 69.82% increase in specific energy absorption capacity for the optimized auxetic structure as compared to the basic structure in quasi-static compressive loading. In high-velocity impact, the sandwich panel with the optimal auxetic core outperforms the one with the basic core. At velocities more than the minimum perforation velocity, the core contributes about 64%–67% of the total absorbed energy by the sandwich panel. © The Author(s) 2024.
Smart Materials and Structures (09641726) 33(11)
Flexible pressure sensors are needed for future artificial electronic skin applications. Carbon black (CB)-enhanced elastomers are known for their unique conductivity, allowing for special uses in sensor technology. This research analyzes the sensitivity of elastomeric sensors reinforced with CB, under a pre-strained buckle, using a modified percolation network model to enhance performance in sensing applications. The finite element method is employed to analyze the piezoresistive characteristics of the sensors across various thicknesses. The research involves analyzing the strain patterns of buckled piezoresistive sensors when an indenter applies a load, and how this influences the sensors’ resistivity. The mechanical parameter is directly correlated to the sensor sensitivity through the maximum principal strain. The model shows a good agreement with the experimental data. The pressure sensitivity resulting from indenter compressive contact is 0.03 and 0.0061 kPa−1 in the pressure range of 0-1 and 0-5 kPa for wavy and straight 1000 μm buckled sensors, respectively. The results show that the film with 50% taller waves has a 40%-60% narrower pressure sensing ranges. Moreover, results indicate that adding waves to the geometry of the sensor improves the piezoresistive behavior by increasing the relative displacements of edges. Results also reveal more stable performance from fewer waves and a higher working range by thicker sensors. © 2024 IOP Publishing Ltd. All rights, including for text and data mining, AI training, and similar technologies, are reserved.
Mirnezhad m., M. ,
Ansari, R. ,
Falahatgar s.r., S.R. ,
Aghdasi p., P. Surface and Interface Analysis (01422421) 56(10)pp. 681-712
In this study, we introduce a comprehensive investigation into the buckling behavior of carbon nanotubes (CNTs) using a combined approach of quantum mechanics and molecular mechanics methods. A novel aspect of our research lies in the exploration of the quantum effects of fine scaling on the buckling behavior of finite-length nanotubes across various dimensions and chiralities. Specifically, we analyze the critical buckling strain variations in CNTs with distinct lengths, diameters, and chiralities, revealing pronounced differences influenced by atomic arrangement and the type of structure used in nanotube construction. Our findings elucidate that at smaller dimensions, (Formula presented.) nanotubes exhibit a higher critical buckling strain than other chiralities, while zigzag atomic arrangements demonstrate greater resistance to torsional loading at larger diameters. Additionally, we compare the buckling behavior of nanotubes obtained by wrapping armchair and zigzag nanosheets, highlighting differential resistance trends. This research not only underscores the critical role of quantum effects in determining nanotube buckling but also provides valuable insights into the nuanced influences of atomic arrangement and nanosheet type on the mechanical properties of CNTs. Thus, our work contributes a novel perspective to the field, bridging the gap between quantum mechanics and the mechanical behavior of nanostructures, which has significant implications for the design and application of nanoscale materials. © 2024 John Wiley & Sons, Ltd.
Ahmadi m., M. ,
Ansari, R. ,
Hassanzadeh-aghdam, M.K. Journal Of The Brazilian Society Of Mechanical Sciences And Engineering (16785878) 46(6)
Thermoelastic constants seem to be important in designing metal-based composite structures under temperature variations. In the current research, the finite element (FE) model has been utilized as a numerical tool to predict equivalent thermoelastic constants of the aluminum matrix composite (AMC) filled with carbon nanotubes (CNTs). The representative volume element of the model has been constructed such that CNTs are randomly oriented and dispersed into the AMC. As an important microstructural factor involved in the CNT-filled AMC, the interfacial reaction product between the two basic phases which may be generated during the composite fabrication has been taken into account. To understand the effect of critical microstructural factors, the equivalent thermoelastic constant of the CNT-filled AMC has been plotted as a function of the percentage and diameter of the nanotube, as well as the elastic modulus, Poisson’s ratio, thermoelastic property and size of the interfacial region. Since CNTs seldom remain straight inclusions, both straight and wavy configurations of nanotubes have been micromechanically analyzed. When the CNT volume fraction is 5%, the thermoelastic constants of the AMC containing wavy and straight CNTs are 21.8 × 10–6 1/K and 20.6 × 10–6 1/K, respectively. A parametric study has been carried out to understand the role of alignment of CNTs in the AMC thermoelastic constant. It is found when the nanotube content is 5 vol%, the thermoelastic constants of the AMC containing randomly oriented and aligned CNTs are 21.8 × 10–6 1/K and 19.8 × 10–6 1/K, respectively. The FE method has been utilized to estimate the equivalent thermoelastic constants of unidirectionally AMCs reinforced by long and short CNTs with the wavy configuration. Comparisons have been made between the present FE predictions and experiments as well as results of other micromechanics approaches. © The Author(s), under exclusive licence to The Brazilian Society of Mechanical Sciences and Engineering 2024.
Applied Physics A: Materials Science and Processing (14320630) 130(5)
This study employs density functional theory calculations to analyze the structural and mechanical properties of stanene nanosheets (SnNs), including elastic moduli, Poisson’s ratio, and plastic behavior under various loads. Parameters of the Morse potential function governing stanene atom interactions are explored. The nanosheets demonstrate isotropic behavior with minimal discrepancy in Young’s modulus between armchair and zigzag directions. Additionally, a progressive finite element method investigates fracture mechanics, simulating the mechanical response using a modified Morse potential function. The nonlinear stress–strain relationships for both pristine and defective armchair and zigzag stanene nanosheets are elucidated, revealing brittle behavior and slightly higher mechanical properties in armchair stanene. Single-vacancy defects significantly impact mechanical properties of stanene, while Stone–Wales defects have negligible effects. © The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature 2024.
Acta Mechanica (16196937) 235(4)pp. 1887-1909
A micromechanics procedure performed by the finite element method (FEM) was developed for the sake of examining the synergistic effects of carbon nanotubes (CNTs) and graphene nanoplatelets (GNPs) hybrids on the elastic and viscoelastic properties of polymer nanocomposites. The representative volume element (RVE) approach was employed owing to its capability to consider various nano-additives with disparate dimensions and evaluate microstructure-level aspects. Constant-strain minimization method and linear viscoelastic model were utilized to predict components of elastic stiffness and creep compliance tensors. The validity of the proposed model was assessed by comparison with the well-established Halpin–Tsai micromechanical model and available experimental measurements, providing an acceptable agreement. Effects of orientation (random or unidirectional dispersion), volume content, and variation in the length and thickness of the carbonaceous nano-additives on the Young’s modulus, Poisson’s ratio, and creep compliance of CNT/GNP/epoxy nanocomposites were investigated. The results explicitly revealed that the CNT and GNP contributions to the mechanical reinforcement and the creep resistance in polymer are strongly associated with their distribution and volume content within the hosting matrix. Moreover, the outcomes imply that increasing the length of CNT, reducing the thickness of GNP lead to increasing Young’s modulus, and decreasing creep compliance (or increasing creep resistance) of CNT/GNP/epoxy nanocomposites. © The Author(s), under exclusive licence to Springer-Verlag GmbH Austria, part of Springer Nature 2023.
Moradi, A. ,
Ansari, R. ,
Hassanzadeh-aghdam, M.K. ,
Jang, S. European Journal of Mechanics, A/Solids (09977538) 103
Progressive innovations in the field of nanotechnology demonstrate that through the radial growth of aligned carbon nanotubes (CNTs) on the circumferential surfaces of fibers known as fuzzy fibers, the transverse elastic properties of fiber-reinforced composites are notably improved. The main objective of the present work is to numerically examine the effects of using fuzzy fiber-reinforced composite (FFRC) skins on the flexural behavior of sandwich structures. Based on the considered two-stage analysis, in the first instance, the mechanical properties of FFRC are determined by the simplified unit cell (SUC) micromechanical model. Afterward, by simulating the three-point bending test via the finite element method (FEM), major assessments are accomplished to reflect the effects of microstructure-level features, including fiber and CNT volume fractions, CNT/polymer interphase, and CNT diameter, on the bending stiffness and debonding growth between the FFRC skin and polyvinyl chloride (PVC) foam core. The results reveal the satisfactory influence of employing FFRC skins on improving the flexural behavior of sandwich structures. © 2023 Elsevier Masson SAS
Haghgoo, M. ,
Ansari, R. ,
Hassanzadeh-aghdam, M.K. ,
Kim, J. Composites Part A: Applied Science and Manufacturing (1359835X) 185
The percolation inception of CNT-polymer nanocomposites is studied considering the magneto-electric field effects on CNT subbands. The analytical model predicts the electrical conductivity where CNTs are modeled as slender rods with their geometric orientations as randomly distributed or aligned to transfer electrons at tunneling distance range. The tunneling effect takes into account the electron transmission between every linked pair of CNTs when evaluating electrical resistance. The subsequent CNT displacement computation and the resistance change comprise the other phase of the modeling approach. Piezoresistivity results of the analyses agree well with the experimental data when considering tunneling behavior in the percolation transition zone. The magnetic field enhances the field affected subbands and increases the electrical conductivity by enhancing the mobility of the charges. The results reveal that the efficiency of CNT network in transmitting charges is increased with higher aspect ratio CNTs that scaled the sensitivity to lower values. © 2024 Elsevier Ltd
Ansari, R. ,
Ershadi, M.Z. ,
Laskoukalayeh, H.A. ,
Rouhi h., H. AIAA Journal (1533385X) 62(2)pp. 833-841
Based on the first-order shear deformation theory (FSDT), the large-amplitude vibration behavior of shallow spherical shells made of functionally graded materials (FGMs) due to the rapid decrease of temperature (cooling shock) is investigated. FGM is assumed to be a mixture of stainless steel and low-carbon steel whose properties are considered temperature dependent and are estimated based on the power-law model. According to FSDT and von Kármán assumptions, the governing equations of motion in conjunction with corresponding boundary conditions are obtained using Hamilton’s principle. The temperature distribution is also achieved by means of the 1D Fourier transient heat conduction equation, considering two time-dependent thermal loading scenarios. The considered thermal boundary conditions allow that a temperature difference is created with a time delay for the structure under cooling shock. Also, the results of recent experiments are employed to estimate the temperature-dependent properties of structures. In the solution approach, the generalized differential quadrature method and the Newmark-beta integration scheme are utilized. Selected numerical results are presented to study the effects of thermal load rapidity time, geometry, magnitude of thermal load, and material gradient index on the thermally induced vibrations of spherical shells. Stresses generated in the shell due to the thermally induced vibrations are also investigated. © 2023 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.
Moradi, A. ,
Ansari, R. ,
Hassanzadeh-aghdam, M.K. ,
Jang, S. European Journal of Mechanics, A/Solids (09977538) 107
Stimuli-responsive shape memory polymer (SMP) nanocomposites, characterized by their shape memory capability and customizable properties, have significantly expanded their range of applications when compared to pristine SMPs. This pioneering paper is centered on describing an efficient numerical approach for evaluating the thermomechanical behavior of ternary acrylate-based SMP nanocomposites containing carbon nanotube (CNT) and graphene nanoplatelet (GNP) hybrids. To this aim, a micromechanical procedure based on thermo-visco-hyperelastic constitutive model, which aids in avoiding employing intricate user-defined material subroutines, is developed through the finite element method (FEM). The parameters required for satisfying the governing equations of the rheological model, including thermal expansion and Prony series coefficients, plus Williams-Landel-Ferry equation and Neo-Hookean strain energy function parameters, are derived from accessible experiments to assign SMP properties. A Python-based script is implemented in a stochastic-iterative process to generate appropriate periodic representative volume elements (RVEs) with various microstructures. Thereupon, thermomechanical shape memory cycles in uniaxial tension are simulated by creating loading, cooling, unloading, and heating steps in the Abaqus solver. Following achieving satisfactory agreement between the presented scheme and experimental measurements, case studies are performed to reflect the influences of dispersion type, volume fraction, and geometry of carbonaceous nanofillers, as well as the contribution of nanofiller/matrix interphase region, upon stress-free/shape-recovery and fixed-strain/stress-recovery thermomechanical cycles. © 2024 Elsevier Masson SAS
Aghdasi p., P. ,
Yousefi, S. ,
Ansari, R. ,
Bagheri tagani m., Journal of Physics and Chemistry of Solids (00223697) 191
This study investigates the impact of doping with carbon (C), fluorine (F), and phosphorus (P) atoms on the structural and mechanical properties of 2 × 2 and 3 × 3 ZnO monolayers using Density Functional Theory (DFT) calculations. Our analysis reveals a notable decrease in both the elastic and bulk moduli of the monolayers upon doping, with the most significant reduction observed in the P-doped structure. For the pristine structure, the elastic modulus is measured at 78.84 N/m for the 2×2 monolayer and 79.46 N/m for the 3×3 monolayer, while the bulk modulus is 62.47 N/m and 63.94 N/m, respectively. Following P doping, the elastic modulus decreases by 56.02 % (34.67 N/m) in the 2 × 2 monolayer and 46.40 % (42.59 N/m) in the 3 × 3 monolayer. Similarly, the bulk modulus experiences substantial decreases of 53.09 % (29.30 N/m) in the 2 × 2 monolayer and 42.96 % (36.47 N/m) in the 3×3 monolayer upon P doping. Additionally, C and F doping result in reductions of 26.10 % and 11.04 % in the elastic modulus of the 2×2 monolayer and 26.27 % and 10.92 % in the 3×3 monolayer, respectively. The corresponding bulk modulus reductions are 14.51 % and 10.79 % in the 2×2 monolayer and 20.12 % and 11.15 % in the 3×3 monolayer, respectively. These findings underscore the considerable influence of various dopants on the mechanical characteristics of ZnO nanosheets, with P doping inducing the most significant reductions in both elastic and bulk moduli, suggesting its efficacy in tuning the mechanical properties of ZnO nanosheets for diverse applications. © 2024 Elsevier Ltd
Nickabadi, S. ,
Ansari, R. ,
Golmohammadi b., ,
Aghdasi p., P. Scientific Reports (20452322) 14(1)
A three-dimensional finite element model is used to investigate the vibrational properties of double-walled silicon carbide nano-cones with various dimensions. The dependence of the vibrational properties of double-walled silicon carbide nano-cones on their length, apex angles and boundary conditions are evaluated. Current model consists a combination of beam and spring elements that simulates the interatomic interactions of bonding and nonbonding. The Lennard–Jones potential is employed to model the interactions between two non-bonding atoms. The fundamental frequency and mode shape of the double-walled silicon carbide nano-cones are calculated. © The Author(s) 2024.
Mechanics of Advanced Materials and Structures (15210596) 30(24)pp. 5159-5175
A two-stage molecular dynamics (MD)-finite element (FE) modeling method is developed based on the concepts of representative volume element (RVE) and equivalent solid fibers (ESFs) containing functionalized carbon nanotubes (ESFs-fCNTs). First, the influences of nanotubes’ chirality, different percent of functionalization ((Formula presented.)), various functional atoms, and polymers on the tensile and shear properties of the fCNTs inserted into the polymer matrix (fCNTs/polymer) are discovered using MD simulations. Then, using MD information as input data, the effective Young’s modulus of polymeric unit cell strengthened by ESFs-fCNTs (ESFs-fCNTs/polymer) is explored through FE modeling. The ratio of effective Young’s modulus of the unit cell ((Formula presented.)) to Young’s modulus of the polymeric cube ((Formula presented.)) is reported and all findings ((Formula presented.)) are compared to the ESFs-pure CNTs/polymer results as well. It is found that longitudinal Young’s modulus ((Formula presented.)) of nanofillers/polymer RVEs affects remarkably the (Formula presented.) of the ESFs-nanofillers/polymer nanocomposites. The (Formula presented.) decreases by increasing the (Formula presented.) Generally, the reinforcing impact of zigzag nanotubes compared to armchair ones on the (Formula presented.) of polymer RVEs is more considerable. Additionally, FE-based results illustrate that as the volume fraction of ESFs ((Formula presented.)) increases, the (Formula presented.) is enhanced. At a specific (Formula presented.) the reinforcing effect of the ESFs-armchair and zigzag fCNTs is more in favor of polyethylene nanocomposites than that of the polypropylene systems. © 2022 Taylor & Francis Group, LLC.
International Journal of Mechanics and Materials in Design (15691713) 19(1)pp. 187-206
The concentration of the present investigation is on the development of a quadrilateral shell element for the deformation analysis of composite laminates. For this purpose, a higher-order shell model with 12 parameters is adopted along with the three-dimensional state of stress. The principle of virtual work is implemented to derive the stiffness matrix and the load vector for the four-node shell element. In order to verify the performance of the higher-order shell element developed herein for the treatment of laminated composites, some benchmarks are solved and compared with solutions available in the literature. © 2022, The Author(s), under exclusive licence to Springer Nature B.V.
Zargar ershadi m., M. ,
Bazdid-vahdati m., ,
Aghaienezhad f., ,
Ansari, R. Thin-Walled Structures (02638231) 187
In this paper, the effect of growth on the stability of elastic materials is examined through a numerical approach. Growth and resorption are considered to have two main effects from the stability standpoint. Corresponding to the change in mass, the geometry of a system changes, and the critical length of the system can be modified. In addition, the growth of the material may be affected by the stress, yet it may also impose residual stresses. As a result, the material is either stabilized or destabilized by these stresses. As a general framework for the description of elastic properties, the theory of finite elasticity is employed to investigate the growth of elastic materials. Growth is taken into account through matrix multiplication of the deformation gradient. The formalism of incremental deformation is adopted to consider growth effects. Using this formalism, the stability of growing neo-Hookean incompressible cylindrical and spherical shells under external pressure is considered. Firstly, the incremental equilibrium equations and the corresponding boundary conditions for the incompressible growing shells are summarized and afterward employed in order to analyze the behavior of spherical and cylindrical shells subjected to external pressure. The generalized differential quadrature method (GDQ) is utilized to solve the eigenvalue problem that results from a linear bifurcation analysis. It is shown that this numerical method can be efficiently utilized to solve the considered problem. The results are in full agreement with the previously obtained results. In the presence of external radial pressure, an elastic shell will buckle circumferentially to a noncircular cross-section. A change in thickness due to the growth can significantly affect buckling, both in terms of the critical pressure and the buckling pattern. Finally, the effects of the thickness ratio A1/A2, mode number n, and the growth parameter γ are studied on the shell's stability. © 2023
European Physical Journal Plus (21905444) 138(1)
This paper presents two hyperelastic models for the micromorphic hyperelasticity which can be efficiently utilized for materials with high dependence on the microdeformation gradient. To this end, two new microdeformation gradient-based strain measures are introduced and used in hyperelastic formulation. The developed formulation for the micromorphic hyperelasticity makes it possible to define hyperelastic functions whose dependency on the microdeformation gradient can be clearly discussed. Also, based on the proposed formulation, any kind of hyperelastic models can be formulated using the defined strain measures. © 2023, The Author(s), under exclusive licence to Società Italiana di Fisica and Springer-Verlag GmbH Germany, part of Springer Nature.
Ansari, R. ,
Zargar ershadi m., M. ,
Oskouie, M.F. ,
Rouhi h., H. Acta Mechanica (16196937) 234(10)pp. 5115-5129
In this paper, a novel numerical approach is proposed to study the geometrically nonlinear large-amplitude vibrations of circular plates subjected to hygrothermal loading resting on an elastic foundation. It is considered that the plates are made of functionally graded (FG) porous materials whose hygro-thermo-mechanical properties are estimated based on the modified Voigt's rule of mixture. Hygroscopic stresses produced because of the nonlinear rise in moisture concentration are taken into account. Moreover, two distribution patterns for porosity (even and uneven) are considered. The Touloukian formula is also employed to assess the temperature-dependence of material properties. Based on the first-order shear deformation plate theory in conjunction with von-Kármán geometrical nonlinear relations, the variational form of the governing equations is derived using Hamilton’s principle. In addition, the effect of the elastic foundation is incorporated into the formulation according to the Winkler-Pasternak model. For solving the problem of nonlinear vibrations, the generalized differential quadrature, variational differential quadrature, and Newmark-beta integration methods are utilized. The influences of important parameters such as temperature distribution, porosity volume fraction, moisture concentration, elastic foundation parameters and FG index on the geometrically nonlinear vibrations of FG porous plates with different boundary conditions induced by hygro-thermal loadings are analyzed. © 2023, The Author(s), under exclusive licence to Springer-Verlag GmbH Austria, part of Springer Nature.
Soleimani m., ,
Gholami, R. ,
Alijani a., ,
Ansari, R. Thin-Walled Structures (02638231) 193
In this study, an analytical solution is provided to present the stress and strain analyses of the multi-layered filament-wound composite (MLF-WC) pipes subjected to the cyclic internal pressure and cyclic thermal loading in hygrothermal environment. The MLF-WC pipe is made of anisotropic, homogeneous and linear elastic materials. It is assumed that the material properties are temperature-independent. Also, applied cyclic loadings are independent of the tangential and axial coordinates. Using the three-dimensional anisotropic elasticity, time-dependent analytical expressions are provided for the stresses, strains and displacements. The accuracy of present analytical approach and numerical results is verified by comparison with those given in literature. It is remarked that the developed analytical solution can be used for the dynamic analysis of functionally graded pipes and pressure vessels under the cyclic loadings. Moreover, through the numerical results, it is found that stacking sequence has a considerable effect on the distributions of shear strain and stress. Furthermore, for the MLF-WC pipe under simultaneous cyclic internal pressure and cyclic thermal loading, the mean amplitudes of the cyclic loadings have a significant effect on the sign of axial strain. © 2023 Elsevier Ltd
Haghgoo, M. ,
Ansari, R. ,
Hassanzadeh-aghdam, M.K. ,
Jang, S. ,
Nankali, M. Composites Part A: Applied Science and Manufacturing (1359835X) 173
An analytical model is developed to predict the piezoresistive sensitivity of nanocomposite strain sensors considering physical properties of carbon nanotubes (CNTs) and carbon blacks (CBs) such as the orientation state, aspect ratio, waviness factor, and agglomeration. A Monte Carlo simulation approach is used to disperse hybrid CNTs/CBs into the matrix. The percolation model is used to introduce the percolation phenomenon into the nanocomposites. Afterward, the piezoresistive property of hybrid nanocomposites is determined using updated fillers’ positions after a stretch in a specific direction of nanocomposites. The nanocomposite resistivity is explored as a function of nanofiller volume fraction. The verification is accomplished by comparing model results with experiments. CNTs with higher aspect ratios and lower waviness factors have a beneficial effect on the electrical properties of hybrid nanocomposites. A good combination of conductive fillers leads to a better piezoresistive response, while a further increase in CB volume fraction cannot be beneficial. © 2023 Elsevier Ltd
Mechanics Based Design of Structures and Machines (15397742) 51(4)pp. 2177-2199
This study presents an analytical solution approach to examine the nonlinear vibration of geometrically imperfect functionally graded porous circular cylindrical shells reinforced with graphene platelets (GPL) surrounded on an elastic foundation. First-order shear deformation theory is employed to formulate the considered problem. Four porosity distributions and four GPLs dispersion patterns are considered which vary through the thickness direction. The effective mechanical properties of considered functionally graded graphene platelet-reinforced porous nanocomposites are characterized via a micromechanical model. Governing equations are derived by Hamilton’s principle and then were transformed into a set of ordinary differential equations using the Galerkin method. Afterward, the nonlinear frequency response curves are obtained with the use of the method of multiple scales. Numerical results are provided to explore the effect of parameters such as initial imperfection, geometry, porous distribution, porosity coefficient, and GPLs’ scheme and weight fraction on the nonlinear frequency-response curve. © 2021 Taylor & Francis Group, LLC.
JVC/Journal of Vibration and Control (10775463) 29(11-12)pp. 2868-2877
The purpose of this article is the comprehensive analysis of free vibration of beam-type liquid micro-pump with a free boundary approach. Besides the liquid loading on the micro-beam, the kinematic compatibility between liquid and micro-beam is modeled according to the free boundaries. Galerkin and separation of variables methods are employed to solve these equations. Based on the nonlinear nature of the equations, the Newmark method is applied to obtain the normal frequencies, mode shapes, and the fluid oscillation of the coupled system. The aim of this model is to achieve the exact results for the small oscillations of micro-beam in the liquid container. Comparing the free and fixed boundary method reveals that for small oscillation of Euler–Bernoulli micro-beam, there is a slight deviation on the natural frequency, which can be negligible. © The Author(s) 2022.
European Physical Journal Plus (21905444) 138(3)
Free vibration of single-layered graphene sheets (SLGSs) subjected to compressive in-plane loads and embedded in a Winkler–Pasternak elastic medium in the pre- and post-buckled configurations is examined herein. To consider both geometric and material nonlinearities and include the size-dependent mechanical behavior of small-scale structures without taking any additional phenomenological parameters into account, the high-order Cauchy-Born (HCB) method, hyperelastic membrane and second gradient elasticity theory are used for providing mathematical formulation. Also, the variational differential quadrature (VDQ) method and Hamilton’s principles are applied to provide a set of discretized governing equations of motion. To evaluate the free vibration of SLGSs in post-buckling domain, first, the post-buckling problem corresponding to the considered system is solved. Then, by assuming a small disturbance about the equilibrium condition, the frequency response of SLGSs is obtained as a function of the applied in-plane load. In numerical results, the effects of various parameters such as geometry, elastic foundation and boundary conditions are highlighted and discussed in detail. © 2023, The Author(s), under exclusive licence to Società Italiana di Fisica and Springer-Verlag GmbH Germany, part of Springer Nature.
Journal of Strain Analysis for Engineering Design (03093247) 58(1)pp. 17-25
The nonlocal theory is commonly applied for nanomaterials due to its capability in considering size influences. Available studies have shown that the differential version of this theory is not suitable for some problems such as bending of cantilever nanobeams, and the integral version must be used to avoid obtaining inconsistent results. Therefore, an attempt is made in this paper to propose an efficient variational formulation based on the integral nonlocal model for the analysis of nanobeams. The formulation is developed in a general form so that it can be used for arbitrary kernel functions. The nanobeams are modeled using the Bernoulli-Euler beam theory, and their bending behavior is analyzed. Derivation of governing equations is performed according to an energy-based approach. Also, a numerical approach based on the Rayleigh-Ritz method is developed for the solution of problem. Moreover, the results of integral and differential models are compared. It is revealed that by the proposed numerical solution, the paradox in the behavior of nanocantilever is resolved. © IMechE 2022.
Journal of Alloys and Compounds (09258388) 951
This study investigates the effectiveness of CoS2/PPy nanocomposites as electrode materials for supercapacitors. We performed a simple and effective one-step hydrothermal fabrication of these nanostructures on nickel foam as substrate. After accurate characterization, electrochemical studies were performed using various techniques, such as cyclic voltammetry (CV), galvanostatic discharge (GCD), and electrochemical impedance spectroscopy (EIS). The result shows excellent electrochemical behaviour of the synthesized electrode with a specific capacitance of 605.2 C g−1 at a current density of 1 A g−1. Moreover, considerable capacitance retention (∼90.9% after 5000 cycles) was obtained. Next, an asymmetric supercapacitor was developed using a prepared electrode and activated carbon (AC /Ni foam) as cathode and anode, respectively. The device showed a high specific energy of 88.07 Wh kg−1 with a significant power of 4.95 kW kg−1 at an operating voltage of These unexpected results indicate that the CoS2/PPy nanostructure has the potential to become a promising electrode for energy storage systems. © 2023 Elsevier B.V.
Haghgoo, M. ,
Ansari, R. ,
Jang, S. ,
Hassanzadeh-aghdam, M.K. ,
Nankali, M. Composites Part A: Applied Science and Manufacturing (1359835X) 166
The thermo-resistive and piezoresistive responses of carbon nanotube (CNT)/graphene nanoplatelet (GNP) polymer-based nanocomposites are analytically investigated. The 3D representative volume element is generated by the Monte Carlo approach to incorporate the random distribution of nanofillers. The Monte Carlo approach is paired with the percolation model to investigate the percolation behavior of the nanocomposite. The validity of the analytical model is verified by comparing the predicted results with the experimental data. The Poisson's ratio and height of barrier potential influence on the piezoresistivity of nanocomposite are studied. Analytical results determine the aspect ratio and influence of carbon nanotube degree of orientation on thermoresistivity of nanocomposite. The effects of intrinsic and physical properties of GNPs on resistivity change with temperature are investigated. It is found that nanocomposite filled with CNTs presented lower percolation threshold than those filled with GNPs. The results also revealed that the filler alignment caused a higher piezoresistivity. © 2022 Elsevier Ltd
International Journal of Structural Stability and Dynamics (02194554) 23(3)
In this paper, the dynamic buckling of functionally graded (FG) porous shallow arches under hygro-thermal loading is studied through a numerical approach. Even and uneven porosity imperfections, hygroscopic stresses generated due to the nonlinear rise in moisture concentration, and the temperature dependence of material properties are all taken into account. The transient heat conduction equation is solved to derive the temperature profile. Hygro-thermo-mechanical properties of the arch are obtained applying the modified Voigt's rule of mixture. The first-order shear deformation theory, the von-Kármán geometrical nonlinearity assumption, and the hygro-thermal strains are considered concomitantly to derive the equations of motions based on Hamilton's principle. The generalized differential quadrature method (GDQM) and Newmark-beta integration schemes are also employed in conjunction with an iterative approach to solve the set of nonlinear governing differential equations of motion. The Budiansky-Hutchinson stability criterion is utilized to capture the dynamic buckling temperature of the structure. A parametric study is conducted in order to investigate the effects of porosity distribution, FG index, geometrical parameters, hygroscopic loading, and thermal/mechanical boundary conditions on arch's dynamic buckling temperature. © 2023 World Scientific Publishing Company.
Keramati y., Y. ,
Ansari, R. ,
Hassanzadeh-aghdam, M.K. Journal of Intelligent Material Systems and Structures (15308138) 34(13)pp. 1548-1560
This research investigates the effect of adding graphene nano-sheets (GNSs) on the elastic and piezoelectric responses of PZT-7A piezoelectric fiber/polyimide hybrid composites. The constructional feature of this hybrid composite is such that unidirectional PZT-7A fibers are embedded into the GNS-filled polyimide material. A nested micromechanical modeling strategy based on the Mori-Tanaka scheme is developed to predict the effective properties of PZT-7A/GNS/polyimide hybrid composites. Parametric studies are performed in order to examine the influences of volume fraction, agglomeration and rolling-up of GNSs, and PZT-7A volume fraction on the piezoelectric hybrid composite coefficients. The results indicate that the elastic and piezoelectric properties of PZT-7A/polyimide composites can be improved by the uniform dispersion of GNSs. However, it is observed that the formation of GNS agglomeration into the polyimide matrix has a serious negative effect on the equivalent properties of piezoelectric hybrid composites. The present predictions are also compared with other results reported in the literature. It is believed that the modeling approach and outcomes of this research may help to design these kinds of novel and highly promising piezoelectric hybrid composites. © The Author(s) 2023.
Silicon (18769918) 15(11)pp. 4795-4809
A molecular dynamics (MD)-finite element (FE) modeling scheme is proposed to study the effective Young’s modulus of polymer nanocomposites reinforced by functionalized silicon carbide nanotubes (fSiCNTs). By evaluating the tensile and shear properties of the polymer matrix strengthened by hydroxyl (O–H)-, fluorine (F)-, and hydrogen (H)-fSiCNTs (O-, F-, and H-fSiCNT/polymer) through MD simulations, FE modeling with the consideration of equivalent solid fibers (ESFs) is conducted and the ratio of effective Young’s modulus of the unit cell (E UC) to Young’s modulus of the polymer matrix (E P) is reported. The influence of the chirality, and chemical functionalization of nanotubes along with the effects of the volume fraction of the ESFs, and polymer materials on the E UC are discovered. The results show that the random dispersion of ESFs containing armchair fSiCNTs (ESFs-armchair fSiCNTs) within the polymers (ESFs-armchair fSiCNTs/polymer) instead of the ESFs-pure armchair fSiCNTs leads to reducing the E UC. In every ESFs volume fraction (ν f), the reinforcement impact of the ESFs-armchair and zigzag fSiCNTs on the polyethylene (PE) is more significant in comparison with the polypropylene (PP). Using the ESFs-zigzag H- and F-fSiCNTs/PP instead of the ESFs-pure zigzag SiCNTs/PP decreases EUC/EP, while at the ESFs’ ν f over 10%, the EUC/EP of the ESFs-zigzag O-fSiCNTs/PP is higher than that of the ESFs-pure zigzag SiCNTs/PP. The ESFs-zigzag H- and F-fSiCNTs/PE as compared to the ESFs-pure zigzag SiCNTs/PE are experienced larger effective elastic moduli, however, only at the ESFs’ ν f of 50%, the reinforcing impact of the ESFs-zigzag O-fSiCNTs within the PE is more considerable than that of the ESFs-pure zigzag SiCNTs. © 2023, The Author(s), under exclusive licence to Springer Nature B.V.
Micro and Nanostructures (27730123) 184
The density functional theory is utilized to investigate elastic and plastic properties of zirconium disulfide (ZrS2) nanosheet subjected to a uniform external electric field up to 4 [Formula presented]. In this respect, firstly, unit cell dimensions, bond lengths and bond angles are obtained by optimizing the unit cell of ZrS2nanosheet, and the most stable configuration is considered for the nanostructure accordingly. Then, by applying uniaxial and biaxial tensions on the nanosheet under a uniform external electric field, Young's and bulk moduli are computed, respectively. Finally, the applied strain is extended to the plastic region to evaluate the effect of external electric field on the first and second critical strains. It is shown that applying external electric field results in increasing Young's modulus of the nanosheet. However, the bulk modulus increases up to 2 [Formula presented] and deceases afterwards. Besides, the first and second critical strains, which are respectively used to show the end of harmonic and inharmonic regions, decrease in the presence of the external electric field while the difference between them is not affected by the external electric field. Investigating the elastic and plastic properties of zirconium disulfide under an external electric field is important for both fundamental research and practical applications. It can help us develop new materials with tunable properties, optimize their performance in various devices, and contribute to the development of cutting-edge technologies © 2023 Elsevier Ltd
Acta Mechanica (16196937) 234(7)pp. 3061-3079
The focus of the current work is on the large deformation analysis of shells made of a transversely isotropic material. For this purpose, a higher-order shell model is adopted and strains are derived and subsequently the stress field of a hyperelastic medium is extracted. Then, by taking advantage of the principle of virtual work, the so-called weak form is obtained. A four-node shell element is developed enriched by remedies for alleviation of locking incorporating transverse shear, membrane and curvature-thickness locking for a compressible anisotropic medium. Finally, some examples are addressed to show the performance of the proposed element as well as anisotropy effects. © 2023, The Author(s), under exclusive licence to Springer-Verlag GmbH Austria, part of Springer Nature.
Eghbalian, M. ,
Ansari, R. ,
Bidgoli, M.O. ,
Rouhi, S. Journal of The Institution of Engineers (India): Series D (22502130) 104(2)pp. 609-622
The present study focuses on the characterization of directional mechanical properties of the polymer matrix reinforced with waviness carbon nanotubes (CNTs) by the finite element method. Young’s and shear elastic modulus in three dimensions have been investigated for representative volume element including straight and waviness (5,5) and (7,7) CNTs with considering the interfacial interaction. These mechanical properties with the alteration of the different parameters such as the number of curves of a CNT, diameter, and length to diameter ratio (L/ D) have been evaluated. The results show that the number of curves, and overall assuming a CNT in its natural state (more curves), significantly impact the longitudinal and directional elastic modulus of nanocomposites. Most outcomes confirm that the transverse Young's and shear elastic modulus of nanocomposites grow and reduce by adding the number of curves and the L/D ratio of CNTs, correspondingly. In addition, the opposite effect is observed in the longitudinal direction for Young’s modulus. © 2022, The Institution of Engineers (India).
Engineering Analysis with Boundary Elements (09557997) 152pp. 66-82
A novel numerical strategy is developed in this article to study the free vibrations of hyperelastic micromorphic continua under bending load. In the proposed approach, the variational differential quadrature (VDQ) method and the idea of position transformation are used. The 3D micromorphic hyperelasticity is first formulated via vector-matrix relations which can be readily utilized in the coding process of numerical methods. The present numerical approach is able to address problems with irregular domains. To this end, the domain of elements is transformed into a regular one by the technique of mapping of position field based on the finite element shape functions. Being locking-free, simple implementation, computational efficiency and fast convergence rate are other features of the present variational approach. Three numerical examples including rectangular, sector and circular plates under bending load are considered whose free vibration behavior is analyzed. It is shown that the method is capable of predicting the relation between natural frequencies of micromorphic hyperelastic continua with load factor in an efficient way. The effects of internal length scale, scale-transition parameter and mode transition on the results are investigated. © 2023 Elsevier Ltd
Journal of Strain Analysis for Engineering Design (03093247) 58(6)pp. 455-463
Several non-classical elasticity theories are used for considering the size-dependent behavior of structures at small scales. The nonlocal theory is widely used to reflect the softening behavior of material at small scales, and theories like the strain gradient theory are employed to reflect the hardening behavior. In this article, the most general form of integral strain- and stress-driven nonlocal models with two nonlocal parameters is developed which is able to consider both hardening and softening influences simultaneously. To this end, it is considered that the stress field at the entire points of the domain is a function of strain field of the entire points of the domain. The free vibration problem of first-order shear deformable beams is solved herein. The integral form of governing equations and associated boundary conditions are obtained first, and then directly solved in a numerical approach. Through developing an efficient matrix formulation and using differential and integral matrix operators, the discretized governing equations are obtained. The simultaneous effects of strain- and stress-driven nonlocal parameters on the natural frequencies of fully clamped, fully simply-supported, and clamped-free nanobeams are investigated. The results indicate that the paradox related to the behavior of clamped-free nanobeams is resolved using the presented integral nonlocal formulation. Also, it is revealed that it is possible to find some specific values of nonlocal parameters at which the prediction of hybrid nonlocal model coincides with that of classical elasticity theory. © IMechE 2023.
Rasoolpoor m., ,
Ansari, R. ,
Hassanzadeh-aghdam, M.K. Mechanics Based Design of Structures and Machines (15397742) 51(1)pp. 260-274
Low velocity impact behavior of multi-walled carbon nanotube (MWCNT)-aluminum (Al) nanocomposite plates are investigated. The rule of mixture is employed to obtain the material properties of the nanocomposites. The microstructural features, including amount, aspect ratio, alignment, waviness, and agglomeration of the MWCNTs are considered. The finite element method is used to investigate the plate dynamic behavior. Addition of the MWCNTs increases the contact force and decreases both the plate center deflection and impact duration. A higher volume fraction, higher aspect ratio, straight shape, and a uniform dispersion of MWCNTs can cause a lesser center deflection of the nanocomposite plates. © 2020 Taylor & Francis Group, LLC.
Ansari, R. ,
Hassanzadeh-aghdam, M.K. ,
Pouyanmehr, R. ,
Umer, U. ,
Haider abidi, M. ,
Alkhalefah, H. Journal of Composite Materials (00219983) 57(21)pp. 3365-3376
Various types of batteries are produced to support years of service for implantable medical devices. Evaluation of internal stresses in nanoparticle-contained electrodes for lithium-ion batteries (LIBs) is a fundamental step toward enhancing their durability. In this research, diffusion induced stresses (DISs) in the bilayer electrode consisted of the carbon nanotube (CNT)-aluminum (Al) nanocomposite active plate bonded to the current collector are investigated. Modeling the DIS is performed by applying the initial stretching on the CNT-Al active plate. Effective properties of CNT-filled Al nanocomposites are calculated using micromechanics models in which the formation of interfacial carbide between the Al and CNT is considered. The role of important microstructural features including amount, length, diameters, curved structure and dispersion type of CNTs, and the thickness and property of interphase in DISs is examined to provide design insights for LIB electrodes. The blending of straight CNTs with a high aspect ratio significantly reduces the tensile stress in the current collector, both compressive and tensile stresses in the nanocomposite active plate and especially the stress drop at the collector/plate interface. Moreover, the DISs can be alleviated by the formation of a stiff and thick interphase between the Al and nanotubes. The CNT-contained electrode with a stretched active plate exhibits lower internal stresses. © The Author(s) 2023.
Pakseresht m., M. ,
Ansari, R. ,
Hassanzadeh-aghdam, M.K. Mechanics Based Design of Structures and Machines (15397742) 51(2)pp. 841-854
Titanium-based composites with their desirable and great mechanical properties are in high demand. One of the main problems that arise in this field is the chemical reactions that appear between strengthening the material and the matrix that usually undermines the integrity of the composite. This problem will result in dangerous defects such as debonding or degradation of the properties. In this work, a coating solution is presented; a similar process as discussed in the literature yet analytically different. The coating is commonly used for protecting and preserving the reinforcing material’s surface which is in contact with the matrix. Herein, a titanium metal matrix composite reinforced with carbon-coated SiC particles is discussed. Mori-Tanaka method was utilized to firstly determine the properties of the inclusion which is the carbon-coated SiC particle and then using the results based on the thickness of the coating and volume fraction of inclusions, calculating the overall properties of the composite. An incremental method was employed to then calculate the stress-strain curve of the said material. The results obtained were in good agreement with the experimental data. The negative effect of the carbon coating on the elastic properties of the SiC/titanium composite was observed as the coating layer thickness increased. The same thing was observed in the stress-strain curve in the slope of the elastic zone and work hardening growth in the plastic zone. © 2020 Taylor & Francis Group, LLC.
Acta Mechanica (16196937) 234(10)pp. 4535-4557
This paper presents a size-dependent study on the free vibration behaviour of the functionally graded (FG) porous curved microbeams. Based on the different higher-order shear deformation models and the modified strain gradient theory, the governing equations are derived using Hamilton’s principle. Then, the isogeometric analysis approach is employed to solve these equations. Besides, the material properties and the material length scale parameters (MLSPs) vary along the thickness direction of the FG curved microbeams according to the rule of mixture scheme. Also, two types of porosity distributions across the thickness, including even and uneven, are considered. By increasing the order of the non-uniform rational b-spline (MLSPs) basis functions, the C2-continuity requirement can be easily achieved. To establish the validity of the proposed method, the present results are compared with those from the previous studies. Finally, the effects of the variable MLSPs, porosity parameter, material gradient indices, curvature and different boundary conditions on free vibration response of circular, elliptical and parabolic FG porous microbeams are investigated. The obtained results reveal that the size-dependent effects increase the natural frequency as well as porosity decreases it because of decreasing the stiffness. © 2023, The Author(s), under exclusive licence to Springer-Verlag GmbH Austria, part of Springer Nature.
Ansari, R. ,
Hassani r., R. ,
Gholami y., Y. ,
Rouhi h., H. Engineering Analysis with Boundary Elements (09557997) 146pp. 306-317
Shell-type structures are frequently used in aerospace, marine and civil engineering. In this paper, a numerical approach called as VDQ-transformed is introduced to analyze the large deformations of hyperelastic shell-type structures based on the Saint Venant–Kirchhoff constitutive model in the context of three-dimensional (3D) nonlinear elasticity. According to the Euler–Lagrange description, the kinetic first Piola-Kirchhoff tensor and kinematic deformation gradient tensor are considered for the stress and strain measures in the formulation. By replacing the tensor form of formulations with matricized ones, the governing equations are written in a novel vector-matrix format which can be readily exploited for programming in numerical approaches. Moreover, discretizing is carried out by the variational differential quadrature (VDQ) method as a point-wise numerical method. To apply the VDQ technique, a transformation is used to map the irregular domain into the regular one. Some well-known benchmark problems for the large deformations of shells are solved to assess the approach. Compact matricized formulation, simple implementation, being locking-free, computational efficiency and fast convergence rate can be mentioned as the main features of the introduced numerical approach. © 2022 Elsevier Ltd
Ahmadi m., M. ,
Ansari, R. ,
Hassanzadeh-aghdam, M.K. Journal Of The Brazilian Society Of Mechanical Sciences And Engineering (16785878) 45(9)
The micromechanical finite element method (FEM) is used to investigate Young’s modulus, yield strength and coefficient of thermal expansion (CTE) of nano-sized silicon carbide (SiC) particle/aluminum (Al) nano-composites (NCs). For this purpose, a 3-dimensional representative volume element containing randomly dispersed SiC nanoparticles is constructed with the precondition of satisfying the periodicity criterion. The effect of the Al4C3 interfacial product formed due to the chemical interaction between the ceramic nanoparticle and metal matrix is numerically evaluated on the NC properties. The results reveal that the mechanical and thermal expanding properties of Al-based composites are improved by the addition of SiC nanoparticles. The increase of uniformly dispersed SiC percentage leads to an increase in Young’s modulus and yield stress and a decrease in the CTE of the Al NC. It is observed that the Al4C3 interfacial product would be beneficial to improve the effective properties of SiC/Al NCs. The higher the interphase thickness is, the better the NC property improvement. In the presence of an interfacial product, the mechanical and thermal expanding properties can be improved by the reduction in the nanoparticle diameter. The reinforcement ratio of Al4C3 turns to be more effective as the SiC diameter decreases. Predictions of the micromechanical FEM are compared with the results of analytical methods and experimental measurements to verify its accuracy. © 2023, The Author(s), under exclusive licence to The Brazilian Society of Mechanical Sciences and Engineering.
Keramati y., Y. ,
Ansari, R. ,
Hassanzadeh-aghdam, M.K. ,
Umer, U. Acta Mechanica (16196937) 234(12)pp. 6251-6270
One mechanism that is expected to play a key role in the enhanced properties of fiber-reinforced composites is adding nano-scale fillers as the second reinforcing agents in the polymer matrix. In this paper, micromechanical analysis of a hybrid smart nanocomposite in which continuous BaTiO3 fibers are embedded into the graphene nanosheet (GNS)-contained epoxy matrix is performed. The Mori–Tanaka model is used at a multi-step procedure to predict the thermal expansion (TE), elastic stiffness and piezoelectric constants of BaTiO3 fiber/graphene hybrid nanocomposites. The micromechanical model has the ability to describe the non-uniform dispersion of GNSs into the epoxy matrix. Further, the effect of the interfacial interaction between the graphene nanoparticles and polymer is captured in the smart nanocomposite modeling through the inclusion of an equivalent solid interphase. Our results indicate that by adding GNSs into the epoxy resin, all stiffness constants, transverse coefficient of TE and piezoelectric constants e31 and e15 of the hybrid nanocomposite are significantly improved. However, non-uniform dispersion and agglomeration of GNSs can decrease the thermo-mechanical and piezoelectric performances of the BaTiO3 fiber/graphene hybrid nanocomposite. In addition, the dependence of effective properties on the interphase characteristics and alignment of GNSs is tested and discussed in details. Comparison studies are carried out in order to show the validity of the present model. © 2023, The Author(s), under exclusive licence to Springer-Verlag GmbH Austria, part of Springer Nature.
Journal of Materials Research and Technology (22387854) 25pp. 5352-5371
This paper aims to understand the effect of friction stir butt welding on the microstructure and mechanical performance, measured in terms of hardness characteristics, transverse tensile test, and shear punch, of dissimilar weld of duplex stainless steel (DSS) and low carbon steel (LCS). The dynamic recrystallization, material intermixing, and atomic interdiffusion between DSS and LCS governed the microstructure of the stirred zone. The stirred zone was free from harmful intermetallic phases like the sigma phase. It was identified that three distinct metallurgical regions feature the stirred zone, including (i) dual-phase zone (DPZ) with an unbalanced fine duplex microstructure of austenite and ferrite, (ii) ferrite phase zone (FPZ) with fine-grained ferrite strengthened by an enhanced Ni and Cr content, (iii) martensite zone (MRZ), which was formed due to the formation of thermally unstable austenite at high temperatures due to Cr, Ni, and C interdiffusion between DPZ and FPZ. Furthermore, when LCS was positioned on the advancing side, a higher fraction of martensite was formed in the stirred zone due to the more efficient material mixing. The shear punch test indicated that the shear strength of the stirred zone in the dissimilar welds was ∼130% and ∼16% higher than that in the LCS and DSS base metals, respectively. The contributions of solid solution hardening and grain boundary hardening to the hardness/strength of the stirred zone were elucidated. © 2023 The Authors
Molecular Simulation (08927022) 49(4)pp. 415-426
The tensile properties and fracture mechanism of hydroxyl-functionalized silicon carbide nanotubes (O-fSiCNTs) inserted into polymer matrices are explored and the outcomes are compared to results for the hydroxyl-functionalized carbon nanotubes (O-fCNTs) incorporated in similar matrices. The molecular dynamics (MD) method is used and the simulations are based on the notion of representative volume elements (RVEs). The incorporation of chemisorbed nanotubes in polymers has a profound effect on the enhancement of their mechanical properties. The O-fSiCNTs inside the polyethylene (PE) and polypropylene (PP) (O-fSiCNTs/PE and O-fSiCNTs/PP) possess lower Young’s modulus, maximum stress, and strain energy as compared to the O-fCNTs/PE and O-fCNTs/PP. The zigzag O-fSiCNTs/polymer experiences lower bearable maximum strains in response to imposed loads in comparison with the O-fCNTs/polymer which is opposite to what occurs in the armchair O-fSiCNTs and O-fCNTs/polymer. The more the functionalization degree is, the weaker the structure is and its stiffness, tensile strength, tolerable strain before fracture, and ability to absorption of internal energy decline. Not only are the zigzag O-fSiCNTs/polymer stiffer than the armchair O-fSiCNTs/polymer in every percent of functionalization, but also as compared to the armchair ones, they show a lower decrease in the variation of Young’s modulus with increasing the functionalization percentage. © 2023 Informa UK Limited, trading as Taylor & Francis Group.
Ahmadi m., M. ,
Ansari, R. ,
Hassanzadeh-aghdam, M.K. Journal of Composite Materials (00219983) 57(23)pp. 3675-3684
This paper aims to predict the elastic-viscoplastic curves of unidirectional carbon nanotube (CNT)-reinforced polymer nanocomposites under the multi-axial tensions, including bi-axial transverse-transverse, bi-axial longitudinal-transverse and tri-axial longitudinal-transverse-transverse loadings by the use of finite element (FE) modeling. The role of the interphase between the CNT and polymer matrix as well as the debonding at the CNT/interphase interface in the stress-strain curves of nanocomposites is investigated. The polymer matrix and interphase region are characterized as elastic-viscoplastic materials, while the CNT behaves as the elastic material. The present results in uni-axial loading are compared to the available numerical outcomes for indicating the accuracy of the FE modeling. The simulation of multi-axial load conditions is based on the three-dimensional representative volume element (RVE) of the unidirectional CNT-polymer nanocomposite. The effect of interface strength on the elastic-viscoplastic stress-strain curves is examined under bi-axial and tri-axial loadings. © The Author(s) 2023.
Rezazadeh, H. ,
Zabihi, A. ,
Davodi a.g., ,
Ansari, R. ,
Ahmad, H. ,
Yao, S. Results in Physics (22113797) 49
In this study, disparate analytical methodologies like the tan method, rational Exp-function method, sech method, extended tan method, and sine–cosine method are implemented to solve the double Sine-Gordon equation (DSG). Subsequently, the dynamical attributes of the obtained results have been underlined and depicted in terms of 3D and 2D graphical illustrations, likewise, different soliton solutions such as kink, bright-dark, and bright are depicted under an appropriate selection of parameters, and the existing criteria of these solitons are also given. A Survey of the literature shows that these methodologies are potent enough to extract exact solutions of differential equations applied in engineering mathematics. © 2023 The Authors
Composite Structures (02638223) 307
The concentration of the present study is on the transient dynamic analysis of composite shells given geometric nonlinearity. For this purpose, use is made of a 12-parameter shell model suited for thick composite structures and then strains and stresses are extracted. The so-called weak form is constructed based on the Hamilton's principle and for gaining the solution to the dynamic problem, the nonlinear finite element method, the total Lagrangian scheme, as well as the composite time integration approach are employed. To overcome the numerical anomalies pertaining to the four-node shell element, transverse shear, membrane and curvatures-thickness locking, appropriate approaches are taken into account. Finally, some problems are solved to evaluate the newly developed shell element and a comparison with the data available in the literature is made. © 2022 Elsevier Ltd
Yademellat, H. ,
Ansari, R. ,
Darvizeh a., A. ,
Torabi, J. ,
Zabihi, A. Mechanics Based Design of Structures and Machines (15397742) 51(1)pp. 179-198
This study investigates the size-dependent dynamic pull-in instability of piezoelectrically and electrostatically actuated micro/nanobeams considering the Euler–Bernoulli theory and von-Kármán hypothesis based on the nonlocal strain gradient theory. In this respect, the impacts of flexoelectricity and piezoelectricity are considered using electrical Gibbs-free energy density and the governing equation is acquired with the help of Hamilton's principle for a sandwich beam with elastic core and two piezoelectric layers. In the present model, different nonlinear forces, such as the fringing field, electrostatic, and intermolecular forces are taken into account. Then, the governing equation is converted from partial differential equation into ordinary one by the Galerkin method considering various boundary conditions, subsequently, the homotopy analysis method is applied as an analytical procedure. The results are validated by comparing the linear frequency, nonlinear frequency, and dynamic pull-in voltage with those in the literature. Consequently, the impacts of different parameters including piezoelectric voltage, nonlocal parameter, length scale parameter, initial amplitude, electrostatic force, flexoelectric, and gap to thickness ratio are discussed in detail. © 2020 Taylor & Francis Group, LLC.
Ansari, R. ,
Zargar ershadi m., M. ,
Mirsabetnazar a., A. Engineering Analysis with Boundary Elements (09557997) 152pp. 225-234
In this paper, thermally induced vibrations of beams made of functionally graded materials (FGMs) subjected to cooling shocks are investigated. It is considered that the beam has been made of a mixture of stainless steel (SUS 304) and low-carbon steel (AISI 1020). To model the displacement field, the third-order beam theory, known as the Reddy beam theory (RBT), is used. Material properties depend on temperature and distribution of materials, and this dependence is modeled through the temperature and the location of materials along the thickness direction. Considering the uncoupled thermoelasticity theory, the temperature distribution is obtained using a one-dimensional Fourier-type transient heat conduction equation, and the equations of motion governing the higher-order beam are derived utilizing Hamilton's principle. Solving the equations is done numerically; the generalized differential quadrature method (GDQM) is employed to approximate the spatial derivatives, and the Newton-Raphson scheme is applied to linearize the equations. In addition, for approximation of the time derivatives, the Newmark method is utilized. Subsequently, the effects of various parameters on the non-dimensional lateral deflection of the higher-order beam considering two different types of thermal loading are investigated. A comprehensive parametric study is conducted to study the effects of important parameters including beam thickness, thermal load rapidity time, the amount of applied load, and the FG parameter. © 2023
Ansari, R. ,
Zargar ershadi m., M. ,
Akbardoost laskoukalayeh h., ,
Rouhi h., H. Thin-Walled Structures (02638231) 193
A numerical approach is developed in the present article to study the geometrically nonlinear vibrations of annular sector plates made of functionally graded materials (FGMs) due to being exposed to cooling shock. The first-order shear deformation plate theory (FSDT) is used in the modeling of plate, and the governing equations of motion are derived based on Hamilton's principle considering von Kármán nonlinear kinematic relations. It is also considered that the properties of FGMs are dependent on temperature and distribution of materials. According to the uncoupled thermoelasticity theory, the temperature distribution is obtained via 1D Fourier-type transient heat conduction equation. To numerically solve the problem, the generalized differential quadrature (GDQ) method and Newmark-beta integration scheme are utilized. Considering two different types of thermal loading as cooling shock, the effects of various parameters including thermal load rapidity time, geometry, magnitude of thermal load and material properties on the large-amplitude vibrations of annular sector plates are investigated. © 2023
Ansari, R. ,
Hassani r., R. ,
Gholami y., Y. ,
Rouhi h., H. Structural Engineering and Mechanics (12254568) 85(2)pp. 147-161
Based on the ideas of variational differential quadrature (VDQ) and finite element method (FEM), a numerical approach named as VDQFEM is applied herein to study the large deformations of plate-type structures under static loading with arbitrary shape hole made of functionally graded graphene platelet-reinforced composite (FG-GPLRC) in the context of higher-order shear deformation theory (HSDT). The material properties of composite are approximated based upon the modified Halpin-Tsai model and rule of mixture. Furthermore, various FG distribution patterns are considered along the thickness direction of plate for GPLs. Using novel vector/matrix relations, the governing equations are derived through a variational approach. The matricized formulation can be efficiently employed in the coding process of numerical methods. In VDQFEM, the space domain of structure is first transformed into a number of finite elements. Then, the VDQ discretization technique is implemented within each element. As the last step, the assemblage procedure is performed to derive the set of governing equations which is solved via the pseudo arc-length continuation algorithm. Also, since HSDT is used herein, the mixed formulation approach is proposed to accommodate the continuity of first-order derivatives on the common boundaries of elements. Rectangular and circular plates under various boundary conditions with circular/rectangular/elliptical cutout are selected to generate the numerical results. In the numerical examples, the effects of geometrical properties and reinforcement with GPL on the nonlinear maximum deflection-transverse load amplitude curve are studied. Copyright © 2023 Techno-Press, Ltd.
Haghgoo, M. ,
Alidoust, A. ,
Ansari, R. ,
Hassanzadeh-aghdam, M.K. Sensors and Actuators A: Physical (09244247) 362
The pressure/resistance sensitivity of the GNP elastomeric nanocomposite is investigated using a finite element percolation model. The simulation model creates an elastomeric RVE, including solid GNP disks, and updates the position and direction of GNPs after the applied pressure. The percolation model predicts the tunneling paths between GNP intersections between the two electrodes. The percolation network between electrodes is promoted through the prevalent contact mechanism between GNPs. The developed numerical model simulates the electrical conductivity and pressure/resistance response in a good correlation with experimental data. Results explain the dominant factors of alignment direction and volume fraction on the resistance response. The resistivity of the nanocomposite reduces significantly with critical distance with a reduced variation rate for lower volume fractions. Results indicate linear pressure/resistance sensitivity under a compressed strain up to 0.16. The results reveal a controllable sensitivity through the appropriate choice of GNP alignment direction, aspect ratio, and volume fraction. © 2023 Elsevier B.V.
Materials Chemistry and Physics (02540584) 309
The current work examines the effect of graphene nanoplatelet (GNP) additives upon the electrical conductivity of short carbon fiber (SCF)-reinforced polymer multifunctional composites. GNPs and SCFs are randomly dispersed into the representative volume element of the composite. A multi-step physics-based approach is developed to determine the effective electrical conductivity of SCF/GNP/polymer composites. Outcomes of the current work are compared with the available experimental data and other numerical results to verify its accuracy. Changes in the volume fraction and geometry of multi-scale reinforcements, interphase characteristics, barrier height, nanofiller tunneling distance and fiber material property are considered to reflect the influence of microstructures on the electrical conducing behavior of SCF/GNP/polymer multifunctional composites. It is found that the electrical conductivity of the multifunctional composite enhances by the increase of volume fraction and aspect ratio of GNP as well as the reduction of its thickness. Moreover, the multifunctional composite shows a higher electrical conductivity with the increase of fiber aspect ratio. The electrical conductivity of the SCF/GNP-reinforced composite depends on the interphase such that its value increases by the increase of interphase thickness. The developed method can be adopted to provide useful guidelines for the design and optimization of multifunctional composites filled by hybrid reinforcements. © 2023 Elsevier B.V.
Mohamadnejad zanjani, S. ,
Basti a., A. ,
Ansari, R. Mechanics of Time-Dependent Materials (13852000) 27(4)pp. 1123-1138
The forming limit diagram is one of the efficient tools to investigate the plastic deformation ability of sheet metals. The forming limits for rate-dependent ideal-orientation crystalline materials are anticipated for the entire variety of linear and nonlinear strain paths and the stress-based forming limit diagrams are also studied. For the first time, crystal plasticity forming limit strains and stresses on the combination of different strain paths such as two-step linear paths, nonlinear strain paths, and the prestrain for an ideal orientation is examined. While the forming limit is very sensitive to the strain path, the strain path has a minor effect on stress forming limit diagrams. A rate-dependent crystal plasticity method is used in combination with the Marciniak–Kuczyniski (M–K) method to anticipate forming limits in face-centered cubic crystalline material with Goss, Cube, and Brass orientations. The results show that strain paths greatly affect the forming limits. It is further shown that in the case of an ideal orientation, forming limit stress curves are not entirely path independent. © 2022, The Author(s), under exclusive licence to Springer Nature B.V.
Haghgoo, M. ,
Ansari, R. ,
Hassanzadeh-aghdam, M.K. ,
Jang, S. ,
Nankali, M. Composites Science and Technology (02663538) 243
A 3D Monte Carlo method paired with a percolation model is carried out to predict the electrical resistivity and piezoresistive sensitivity of carbon nanotube (CNT)-polymer piezoresistive sensors. CNTs are randomly dispersed into the insulating layer of a polymer matrix having agglomerated morphologies in some parts. The electrical resistivity of nanocomposite with a defined agglomeration state is determined by considering the tunneling effect between each connected pair of CNTs. The influence of various parameters such as agglomeration radius, percentage, intrinsic properties and geometries of CNTs are investigated. A comparison was made between the analytical results and experimental data. Considering the tunneling behavior in the vicinity of the percolation transition, a good agreement is obtained between the analytical results and experimental data. Monte Carlo simulations indicated that the tunneling resistance with a random distribution of CNTs depends on the level of agglomeration. Results revealed that piezoresistive sensitivity was diminished by larger agglomerations. © 2023 Elsevier Ltd
Zabihi, A. ,
Shaayesteh, M.T. ,
Rezazadeh, H. ,
Ansari, R. ,
Raza, N. ,
Bekir, A. Journal of Nonlinear Optical Physics and Materials (17936624) 32(3)
In this paper, solitons solutions of higher-order dispersive cubic-quintic Schrödinger equationincluding third-order as well as fourth-order derivatives with respect to time, that describes the dynamics of ultrashort pulses in optical fibers are investigated in detail. In this respect,a solution procedure in the locality of applied mathematics called the hyperbolic function method is appliedusing multi-linear variable separation approach (MLVSA). As an outcome, a bunch of soliton solutions isderived in conjunction with plotting dark and periodic wave solutions. The credibility of the results is examined by setting each solution back into its governing equation. Through portraits, different forms of wave solutions are depicted. Moreover, the restrictions on the parameters are also given for the existence of the obtained solutions. © 2023 World Scientific Publishing Company.
Nesarhosseini s., ,
Ansari, R. ,
Oskouie, M.F. ,
Rouhi h., H. Acta Mechanica (16196937) 234(5)pp. 1957-1971
In this paper, the free vibrations of beam-type structures subjected to rapid heating are analyzed within the framework of micropolar thermoelasticity using a novel numerical approach. The equations of motion are derived based on the micropolar elasticity theory and the Timoshenko beam theory using Hamilton’s principle. The transient 1D Fourier-type heat conduction equation is also used as the heat equation. The matrix representation of relations is given which can be efficiently utilized in numerical approaches. Solution in time domain is done by the Newmark algorithm based on the constant average acceleration technique. The generalized differential quadrature and variational differential quadrature techniques are also applied to discretize in space domain. Important effects including those of thermal shock and geometrical parameters on the thermally induced vibrations of micropolar Timoshenko beams with various boundary conditions are investigated. © 2023, The Author(s), under exclusive licence to Springer-Verlag GmbH Austria, part of Springer Nature.
Ansari, R. ,
Hassani r., R. ,
Gholami y., Y. ,
Rouhi h., H. International Journal of Structural Stability and Dynamics (02194554) 23(10)
Using the ideas of variational differential quadrature (VDQ) technique and position transformation, an efficient numerical approach is developed herein in order to address the free vibration problem of compressible and nearly-incompressible solid bodies with arbitrary deformed shape within the framework of 3D hyperelasticity. The 3D hyperelasticity is first formulated by vector-matrix relations with the purpose of applying in coding process. An energy principle together with the Neo-Hookean strain energy function is also employed in the derivation of governing equations. The proposed numerical method is capable of addressing problems with irregular domains. Simple application, being free from the locking problem, and fast convergence rate are the key features of the approach. Hyperelastic rectangular/ sector plates and cylindrical panel subjected to bending load are selected as test problems whose free vibrations are analyzed. The developed numerical method is found to be capable of yielding accurate solutions to the considered problems. Moreover, the effects of mode transition and geometrical properties are investigated in the numerical examples. © 2023 World Scientific Publishing Company.
Nadimi, N. ,
Pouranvari, M. ,
Ansari, R. ,
Pouranvari, M. Journal of Materials Research and Technology (22387854) 26pp. 5549-5565
The fusion zone (FZ) hardness of resistance spot welds is a crucial factor affecting the performance and durability of the welds. Failure mode transition, tendency to fail in interfacial mode, interfacial failure load, and the impact of liquid metal embrittlement cracks on the weld strength are influenced by the FZ hardness. Therefore, accurately predicting the FZ hardness in resistance spot welds made on automotive steels is essential. A simple thermal model is used to calculate the time required for the temperature to drop from 800 °C to 500 °C (Δt[Formula presented]). With the aid of continuous cooling transformation (CCT) diagrams and experimental confirmation, it is shown that in most automotive steels, the FZ exhibits an almost full martensitic microstructure. Generally, the FZ hardness tends to increase in the order of interstitial-free (IF), drawing quality specially killed (DQSK), high strength low alloy (HSLA), ferrite-martensite dual-phase steels, transformation induced plasticity (TRIP), and quench & partitioning (Q&P) steels. To predict the FZ hardness, data-driven regression-based models have been developed based on carbon content, carbon equivalent concept, and the strengthening mechanisms of the martensite. Among these models, the model based on martensite strengthening mechanisms showed the best performance and robustness in estimating the FZ hardness. The assessment of the strengthening mechanism of the FZ showed that most important factors determining the FZ hardness are dislocation hardening due to carbon atoms, interface hardening due to block boundaries, and solid solution hardening due to substitutional alloying elements, respectively. A simple relation is proposed to estimate the load-bearing capacity of automotive steel spot welds during interfacial failure based on the FZ hardness. © 2023 The Author(s)
Materials Chemistry and Physics (02540584) 283
Herein, the effects of halogen and metal atomic adsorption on the mechanical and structural characteristics of silicene are studied using density functional theory (DFT) calculations. Cl, Br, Au, Ca, Ga, Li, and Na atoms are selected as the adsorption atoms. Moreover, the phonon dispersion and electron localization function are investigated to show the stability of considered nanostructures and to visualize the bonding properties, respectively. It is shown that the adsorption leads to decreasing the elastic and bulk moduli of some structures, while it increases them in some other structures. It is seen that except for Ca-adsorbed nanosheet, both the elastic and bulk moduli of all other structures decrease after adsorption. Furthermore, the isotropic behavior of all the studied nanosheets is indicated. The plastic behavior is also analyzed. It is revealed that the second critical strain of all nanosheets, except for SiBr and SiCl, decreases under uniaxial loading. However, under biaxial loading conditions, the second critical strain of Au-, Ca-, and Ga-adsorbed structures decreases, while in other structures (SiBr, SiCl, SiLi, and SiNa) the adsorption increases the yield strain. © 2022 Elsevier B.V.
Aghdasi p., P. ,
Yousefi, S. ,
Ansari, R. ,
Bagheri tagani m., Applied Physics A: Materials Science and Processing (14320630) 128(8)
In this paper, the elastic and plastic properties of 2 × 2 and 3 × 3 pristine and transition metal (TM) doped silicene nanosheets are studied using the density functional theory (DFT) calculations. Cr, Co, Cu, Mn, Ti, V, Zn and Ni atoms are selected as doping atoms. It is observed that Young’s and bulk moduli of both 2 × 2 and 3 × 3 pristine structures decrease when they are affected by the doping atoms. The highest reduction in the Young’s and bulk moduli of the 2 × 2 nanosheets occurs for the Ni-doped structure, and the same reduction is observed for the Ni- and Cu-doped structures in the 3 × 3 nanosheets. In addition, it is shown that all of the investigated structures have an isotropic behavior, since their Young’s moduli have negligible difference along armchair and zigzag directions. Finally, the loading is further increased to investigate the plastic behavior of nanostructures. The results show that the yield strains of all doped nanosheets decrease under uniaxial and biaxial loadings. The highest reduction in the yield strain of the 2 × 2 nanosheets under biaxial loading is observed for Cu, Zn- and Co-doped nanosheets, and in 3 × 3 nanosheets, the highest reduction happens for the Cu- and Zn-doped nanosheets under the same condition. For the yield strain of the 2 × 2 doped nanosheets under the uniaxial loading, the Cu-doped structure experiences the highest reduction, and the highest reduction for the Mn-doped nanosheet under the same condition is observed in 3 × 3 nanosheets. The findings revealed that how electronic configuration of transition metal atom and its electronegativity difference with silicon atom can control the structural and mechanical properties of the nanosheet. © 2022, The Author(s), under exclusive licence to Springer-Verlag GmbH, DE part of Springer Nature.
Diamond and Related Materials (09259635) 125
In this paper, the free vibration of hybrid carbon boron-nitride heteronanotubes (CBNNTs) is analyzed through molecular dynamics (MD) simulations. In the vibration analysis, various CBNNTs (Cx ∣ (BN)y and C-BN models) according to two geometrical arrangements of constituent segments are considered. By introducing vacancy defects in nanotubes, the influence of defects on the vibrational response is studied in terms of the weight percentage and distribution pattern. The highest vibration frequency is reported and CBNNTs' results are compared with those of carbon nanotubes (CNTs) and boron-nitride nanotubes (BNNTs). It is observed that CBNNTs possess natural frequencies which lie between the values for CNTs and BNNTs. The natural frequency is found to be reduced by increasing the defect percentage. At each defect percentage, the defective C-(BN) model I and C1.5 ∣ (BN)1.5 experience almost the same natural frequency in both distribution patterns. Vibration frequencies of defective C-(BN) model II and C4.5 ∣ (BN)4.5 are nearly close together at a defined percentage of defects. Despite the minor differences between natural frequencies in either distribution pattern, regularly defected CNTs tend to have a bit higher frequency than randomly defected CNTs, however, the results are opposite in the regularly and randomly defected BNNTs. Moreover, the C-(BN) model II vibrates at a higher natural frequency than that of the C-(BN) model I. It is found that the vibrational behavior of the C-(BN) model I is mostly affected by the BN segment than the C segment. Further, the natural frequency's drop in the defected C1.5 ∣ (BN)4.5 is found to be more significant than other CBNNTs by rising the defect percentage. C-(BN) model I and defective C-(BN) model I experience higher deformations in comparison with the Cx ∣ (BN)y configurations when vibrating at their natural frequency. © 2022
Haghgoo, M. ,
Ansari, R. ,
Hassanzadeh-aghdam, M.K. ,
Nankali, M. Acta Materialia (13596454) 230
Monte Carlo simulation is paired with a percolation model to analytically investigate the temperature effect and carbon nanotube (CNT) dispersion state on the temperature-dependent piezoresistive conductive network nanocomposite. The charge transport switch from electrical tunneling to elevated temperature quantum tunneling is studied based on a temperature-dependent tunneling model. The percolation network theory searches for the shortest distance of any CNT line segments scattered in the representative volume element to form possible interconnections and tunneling resistance approach evaluates resistivity by recognizing the conductive percolating paths. The effect of different factors such as the height of barrier potential, CNT length, degree of orientation and the cutoff distance on the resistance of the nanocomposite which is mainly caused by the inter-tube tunneling resistance is studied through analytical parametric studies. It is shown that the strain sensitivity of reinforced nanocomposite is increased as a result of the uniform dispersion of short aligned CNTs. © 2022
Roudbari, M.A. ,
Jorshari, T.D. ,
Lü, C. ,
Ansari, R. ,
Kouzani, A.Z. ,
Amabili, M. Thin-Walled Structures (02638231) 170
Recently, the mechanical behavior of micro-/nano-structures has sparked an ongoing debate, which leads to a fundamental question: what steps can be taken to investigate the mechanical characteristics of these structures, and characterize their performance? From the standpoint of the non-classical behavior of materials, size-dependent theories of micro-/nano-structures can be considered to analyze their mechanical behavior. The application of classical theories in the investigation of small-scale structures can lead to inaccurate results. Many studies have been published in the past few years, in which continuum mechanics models have been used to investigate micro-/nano-structures with different geometry such as rods, tubes, beams, plates, and shells. The mechanical behavior of these systems under different loading – resulting in vibration, wave propagation, bending, and buckling phenomena – is the focus of the review covered in this work. The present objective is to provide a detailed survey of the most significant literature on continuum mechanics models of micro-/nano-structures, and thus orient researchers in their future studies in this field of research. © 2021 Elsevier Ltd
Applied Mathematics and Mechanics (English Edition) (02534827) 43(8)pp. 1219-1232
A new numerical approach is presented to compute the large deformations of shell-type structures made of the Saint Venant-Kirchhoff and Neo-Hookean materials based on the seven-parameter shell theory. A work conjugate pair of the first Piola Kirchhoff stress tensor and deformation gradient tensor is considered for the stress and strain measures in the paper. Through introducing the displacement vector, the deformation gradient, and the stress tensor in the Cartesian coordinate system and by means of the chain rule for taking derivative of tensors, the difficulties in using the curvilinear coordinate system are bypassed. The variational differential quadrature (VDQ) method as a pointwise numerical method is also used to discretize the weak form of the governing equations. Being locking-free, the simple implementation, computational efficiency, and fast convergence rate are the main features of the proposed numerical approach. Some well-known benchmark problems are solved to assess the approach. The results indicate that it is capable of addressing the large deformation problems of elastic and hyperelastic shell-type structures efficiently. © 2022, Shanghai University.
Haghgoo, M. ,
Ansari, R. ,
Hassanzadeh-aghdam, M.K. ,
Nankali, M. Journal of Composite Materials (00219983) 56(28)pp. 4339-4361
In this study, the temperature-dependent piezoresistivity of hybrid carbon black (CB)/carbon nanotube (CNT) nanocomposites is studied using a percolation model with a Monte Carlo simulation approach. With this approach, the temperature-dependency of electrical resistivity and the strain sensitivity of the nanocomposite are investigated. In addition, other parameters such as the aspect ratio, dispersion state and dimensions’ effect on piezoresistivity of the compensated stretchable nanocomposite are investigated. By developing a temperature-dependent percolation model, the temperature sensitivity response of nanocomposite is investigated based on defining the temperature coefficient of resistance of CNT and thermal expansion coefficient of polymer. It is found that the dimensional aspects and dispersion state affected the percolation threshold and resistivity. The obtained results also indicated that the piezoresistivity increased with the decrease in the Poisson’s ratio and intrinsic electrical conductivity. Moreover, the predicted results showed high prediction accuracy for temperature-dependence resistivity compared with the existing experimental data. © The Author(s) 2022.
Continuum Mechanics and Thermodynamics (09351175) 34(2)
Presented herein is a numerical variational approach to the two-dimensional (2D) incompressible nonlinear elasticity. The governing equations are derived based upon the minimum total energy principle by considering the displacement and a pressure-like field as the two independent unknowns. The tensor equations are replaced by equations in a novel matrix-vector form. The proposed solution method is based upon the variational differential quadrature (VDQ) method and a transformation procedure. Using the introduced VDQ-based approach, the energy functional is precisely discretized in a direct way. Being locking-free, simple implementation and computational efficiency are the main features of this method. Also, it is free from numerical artifacts and instabilities. Some important problems of 2D incompressible elasticity are addressed to test the method. It is revealed that it can be efficiently utilized to capture the large strains of incompressible solids. © 2021, The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.
Haghgoo, M. ,
Ansari, R. ,
Hassanzadeh-aghdam, M.K. ,
Tian, L. ,
Nankali, M. Composites Part A: Applied Science and Manufacturing (1359835X) 163
Carbon nanotubes (CNTs) are incorporated into a stretchable polymer to determine modified thermo-resistive and piezoresistive responses of a nanocomposite under temperature variation and mechanical strain. Monte Carlo simulation is paired with tunneling model to disperse CNTs into the representative volume element and recognize CNT-to-CNT separation distance to predict the resistance change of nanocomposites subjected to strain. The principle of thermo-electrical properties is studied under thermo-mechanical stimulus. Nanotube reorientation model is used to investigate the influence of CNT's tunneling and state of alignment on the piezoresistive behavior of the nanocomposite. Comparisons between modeling results and experimental data suggested a good agreement. The nearly linear dependence of relative resistance change with strain displayed more sensitivity with shorter CNTs and less sensitivity with higher CNT volume fractions. Relative resistance change with temperature was strongly affected by CNTs’ temperature coefficient of resistance and volume fraction. Such change was more pronounced for the anisotropic nanocomposite. © 2022 Elsevier Ltd
International Journal of Mechanics and Materials in Design (15691713) 18(1)pp. 39-61
A 3D Monte Carlo simulation and percolation network model for hybrid nanocomposites reinforced by carbon nanotubes (CNTs) and carbon black (CB) nanoparticles (NPs) is established to investigate the percolation probability and piezoresistivity considering electron tunneling effect. Firstly, a Monte Carlo algorithm is developed to form a representative volume element filled with randomly oriented CNTs and randomly dispersed CB NPs. Later, a percolation like network model is developed to determine the resistivity between each of CNTs and CB NPs, and then the electrical model based on modified location analysis is employed to calculate the corresponding piezoresistive behavior of hybrid CNT–CB polymer nanocomposites under tension. Tunneling resistance variation with the evolution of the conductive network during the inducing strain leads to non-linear and exponential behavior of relative electrical resistance change with strain. Parametric studies are performed to show the effects of CB volume fraction, size and CNT maximum orientation angle on the percolation probability and piezoresistivity of hybrid CNT–CB polymer nanocomposites. Results indicate that the piezoresistive sensitivity is greatly improved in the nanocomposites with the introduction of hybrid CB NPs/short aligned CNTs. Respecting to piezoresistive sensibility, the gauge factor calculated from the change of resistance as a function of applied strain reaches high value for sensitive piezoresistive sensor with lower Poisson’s ratio and larger diameter of CB NPs. © 2021, The Author(s), under exclusive licence to Springer Nature B.V.
Zabihi, A. ,
Akinshilo, A.T. ,
Rezazadeh, H. ,
Ansari, R. ,
Sobamowo, M.G. ,
Tunç, C. Computational Methods For Differential Equations (23453982) 10(3)pp. 580-594
In this paper, the transport of flow and heat transfer through parallel plates arranged horizontally against each other is studied. The mechanics of fluid transport and heat transfer are formulated utilizing systems of the coupled higher-order numerical model. This governing transport model is investigated by applying the variation of the parameter’s method. Result obtained from the analytical study is reported graphically. It is observed from the generated result that the velocity profile and thermal profile drop by increasing the squeeze parameter. The drop inflow is due to limitations in velocity as plates are close to each other. Also, thermal transfer due to flow pattern causes decreasing boundary layer thickness at the thermal layer, consequently drop in thermal profile. The analytical obtained result from this study is compared with the study in literature for simplified cases, this shows good agreement. The obtained results may therefore provide useful insight to practical applications including food processing, lubrication, and polymer processing industries amongst other relevant applications. © 2022 by the Author(s).
Aryayi, M. ,
Hadavi, M.R. ,
Nickabadi, S. ,
Ansari, R. Journal of Failure Analysis and Prevention (18641245) 22(3)pp. 1144-1150
Pitting corrosion is a typical damage on structures, which causes stiffness reduction and mass loss. These changes affect the vibrational behavior of corroded structures. In this study, a three-dimensional finite element model is used to investigate the influence of pitting on the natural frequencies of transverse vibration of a clamped-free shaft. The results of the finite element numerical simulation are validated by experimental results and the beams analytical methods. The simulation results show that the increase in the amount of corrosion reduces the natural frequencies, but the trend of this change differs for different modes. In addition, the percentage change in the natural frequencies because of the increase in the length of the corroded region and the change of its location depends on the mode shapes. The results also indicate that the corroded surface is effective in the amount of change of transverse natural frequencies of the shaft. © 2022, ASM International.
Mechanics Based Design of Structures and Machines (15397742) 50(2)pp. 588-608
The main subject of this study is the dynamic and static pull-in analyses of rectangular nanoplates made of functionally graded materials based on the nonlocal strain gradient theory compared with the strain gradient theory, Eringen’s differential method, and classical theory considering disparate boundary conditions (BCs). To this end, the governing equation is derived based on Kirchhoff’s plate theory and then, the Galerkin method is implemented to arrive at an ordinary differential equation of second-order in the time domain. The homotopy analysis method is used as an analytical solution methodology to solve the nonlinear ordinary differential equation which is under different nonlinear forces such as intermolecular, electrostatic and hydrostatic one. Likewise, an efficient technique is exerted for omitting secular terms. Accordingly, the dynamic pull-in voltage is obtained for different non-classical continuum theories, material gradient indices, nonlocal parameters and internal length scale parameters. The dynamic and static pull-in instabilities are also compared in the same situation. Additionally, the effects of the nonlocal parameter and internal length scale parameter on the non-dimensional frequency against the initial amplitude, electrostatic force and hydrostatic actuation are explored in disparate boundary conditions. Communicated by Eleonora Tubaldi. © 2020 Taylor & Francis Group, LLC.
Ansari, R. ,
Nesarhosseini s., ,
Oskouie, M.F. ,
Rouhi h., H. International Journal of Structural Stability and Dynamics (02194554) 22(8)
In this paper, the nonlinear thermally induced vibration in rectangular plates made of porous functionally graded materials (FGMs) due to thermal shock is studied based on a new numerical approach. The shear deformation influences are taken into consideration via Mindlin's plate theory. The properties of the materials are also assumed to be temperature- and position-dependent. Moreover, the influence of elastic foundation is captured by the Winkler-Pasternak model. For deriving the governing equations, Hamilton's principle, transient 1D Fourier-type heat conduction equation and von Kármán hypothesis are utilized. The relations of paper are written in a new matricized format for computational aims. The generalized differential quadarature (GDQ) method and Newmark's direct integration scheme are used for solving the heat equation. Furthermore, solving motion equations is done based on the variational differential quadrature (VDQ) formulation. The effects of important parameters including material porosity and elastic foundation on the thermal shock response of porous FG plates are investigated in the numerical results. © 2022 World Scientific Publishing Company.
Engineering with Computers (14355663) 38pp. 43-54
The numerical investigation is performed on the vibration of the higher order shear deformable carbon nanotube reinforced composite (CNTRC) spherical panels subjected to the initial external pressure. The functionally graded nanocomposite is reinforced with the non-uniform distribution of CNTs. The problem is formulated following the higher order shear deformation shell theory (HSDT) within the variational differential quadrature numerical approach. For this purpose, the direct discretization of Hamilton’s principle is carried out with the aid of differential quadrature operators. Derivation of the variational formulation of nanocomposite spherical panels based on the HSDT and studying the effects of external pressure on the vibration behavior are the main novel aspects of this research. Several numerical examples are provided to survey the impacts of geometrical and material factors on the vibration of pressurized functionally graded CNTRC spherical panels. It is shown that the internal pressure has the most influence on the vibrational behavior of the thicker panel. © 2020, Springer-Verlag London Ltd., part of Springer Nature.
Hassanzadeh-aghdam, M.K. ,
Ansari, R. ,
Jamali, J. ,
Mohaddes deylami, H. Journal Of The Brazilian Society Of Mechanical Sciences And Engineering (16785878) 44(8)
A nested micromechanical technique is proposed to predict thermal conductivities of discontinuous silicon carbide (SiC)/graphene nanoplatelet (GNP)-reinforced aluminum matrix multiphase composites (AMMCs). Agglomeration and waviness of GNPs and interfacial thermal resistance (ITR) between the nanofiller and metal matrix are considered to perform a more realistic simulation process. The present predictions are compared with experimental measurements to verify the validity of the micromechanics approach. The effects of volume fraction, waviness, size and nonuniform distribution of GNPs, graphene/metal ITR, volume fraction, length and diameter of discontinuous SiC and SiC/matrix ITR on the AMMC thermal conductivities in the axial and transverse directions are investigated. The results show that heat in discontinuous SiC/metal composites is better transferred by a uniform distribution of GNPs in the metal matrix. The increase in graphene volume fraction leads to an enhancement in the heat transfer capacity for the metal-based multiphase composites. It is found that GNP with higher length and thickness can significantly improve the AMMC thermal conductivities. However, a great decrease in the thermal conductivities is observed by the ITRs and waviness of nano-graphene. Also, formation of GNP agglomeration drastically reduces the AMMC heat transfer capacity. Increasing the length of discontinuous SiC up to a certain value significantly increases the AMMC thermal conductivity in the axial direction, however, it has a negative effect on the transverse thermal conductivity. © 2022, The Author(s), under exclusive licence to The Brazilian Society of Mechanical Sciences and Engineering.
Journal of Molecular Graphics and Modelling (10933263) 111
In the present work, molecular dynamics (MD) simulations are used to investigate the impact behavior of single-walled carbon nanotubes (SWCNTs) with free boundary conditions in two directions, i.e. vertical and horizontal. To consider the effect of consecutive impacts, the number of carbon nanotubes (CNTs) participated in simulations is chosen from two to five in a row. MD results show that adding the number of impacts increases the magnitude of energy loss in both mentioned directions and reduces the maximum impact force in horizontal cases. In addition, by increasing the velocity of striker CNT from 1 km/s to the maximum value which causes any fracture, the effect of initial velocity on the impact properties and also the ultimate initial velocity for each model are investigated. It is demonstrated that the energy loss and the maximum value of impact force increase as the initial velocity of the striker increases. Also, it is found that the impact strength in the vertical direction is higher than that of the horizontal one, while the horizontal CNTs perform better in the absorption of impact energy. Moreover, for all models, the fracture mechanism of CNTs resulting from the impact process is represented and the procedure of failure is explained. © 2021 Elsevier Inc.
Transport In Porous Media (15731634) 142(1-2)pp. 41-62
In this article, the nonlinear hygrothermally induced vibrational behavior of bidirectional functionally graded porous beams is studied through a numerical approach. Two-dimensional material and temperature distributions, even and uneven porosity distributions, temperature-dependent nature of material properties, and hygroscopic effects are all taken into account in studying beam’s lateral deflection. All material properties are assumed to vary along both thickness and axial directions of beam following a modified power-law distribution in terms of volume fractions of the material constituents, which are considered temperature dependent using Touloukian experiments. Beam's upper surface is subjected to a sudden temperature rise, while its lower surface is kept at reference temperature or is thermally adiabatic; meanwhile, left and right boundaries are thermally insulated. Two-dimensional transient heat conduction equation is solved using generalized differential quadrature (GDQ) method for discretizing spatial derivatives, while time derivatives are approximated using Newmark-beta integration method. Nonlinear sinusoidal moisture concentration is assumed through the thickness direction. Governing equations of motion are derived based on Timoshenko beam theory (TBT) and with the assumption of Von-Kármán geometrical nonlinearity, which is solved afterward using an iterative scheme in conjunction with GDQ and Newmark's method. Finally, the effects of porosity volume fractions, porosity cases, thermal boundary conditions, moisture concentration, FG indexes, slenderness ratio, and temperature rise on maximum non-dimensional lateral deflection are investigated considering various boundary conditions. © 2021, The Author(s), under exclusive licence to Springer Nature B.V.
Rezazadeh, H. ,
Sab’u, J. ,
Zabihi, A. ,
Ansari, R. ,
Tunç, C. Nonlinear Studies (21534373) 29(2)pp. 547-559
This article deals with new soliton solutions of the generalized nonlinear Schrödinger equation with variable coefficients by the direct algebraic method. Once the variables of this technique are considered as special values, we could achieve the solitary waves that are unique from those attained by the other methods. It can be inferred that the solution methodology in conjunction with symbolic computing eligible to solve nonlinear partial differential equations precisely. © CSP - Cambridge, UK; I&S - Florida, USA, 2022
Hassanzadeh-aghdam, M.K. ,
Ansari, R. ,
Mohaddes deylami, H. International Journal of Thermal Sciences (12900729) 171
This study comprehensively investigates the thermal transport behavior of unidirectional hybrid composites (UHCs) by means of a micromechanical methodology. The constructional feature of the UHC is that the continuous carbon fibers are embedded in the graphene nano-platelets (GNPs)-modified epoxy resin. The influences of volume fraction, length, thickness, and alignment of GNPs, the interfacial thermal resistance (ITR) between the nano-graphene and polymer matrix, as well as the volume fraction, arrangement type, and off-axis angle of carbon fibers on the thermal conductivities of UHCs are extensively analyzed. Further, the micromechanical model is extended to account the effect of GNP agglomeration on the UHC thermal conductivities. The results show that uniformly dispersed GNPs play a dominant role in improving the UHC thermal conductivity along the transverse direction, while the axial thermal conductivity is insignificantly influenced by the nano-graphene particles. Besides, using the GNPs with a higher aspect ratio (length/thickness) is an efficient manner to obtain much better thermal transport performance for the UHCs. It is observed that the formation of GNP agglomeration within the epoxy resin severely decreases the transverse thermal conductivity. The presence of GNP/epoxy ITR is a lowering factor of the thermal conductivity. As compared to the hexagonal and random arrays, the square array of carbon fibers within the GNP-modified epoxy produces the largest transverse thermal conductivity. On the basis of comparative studies, the model predictions agree very well with the experimental data available in the literature. © 2021 Elsevier Masson SAS
European Physical Journal Plus (21905444) 137(6)
In this paper, the isogeometric analysis based on the non-uniform rational B-spline (NURBS) basis functions is used to study of the bending, buckling and free vibration of the multi-directional functionally graded porous plates with variable thickness. The third-order shear deformation theory is used to account for shear deformation effect, which does not require any shear correction factors. The material properties of the plates are estimated by the rule of mixture and the Mori–Tanaka scheme. The C1 required degree of continuity is easily obtained by increasing the order of the NURBS basis functions. The governing equations of motion are extracted by Hamilton’s principle and then discretised by the isogeometric analysis approach. The effect of different length-to-thickness ratios, material gradations, thickness variations, porosity parameters, and the different boundary conditions on the bending, buckling and free vibration of rectangular, circular and elliptical multi-directional functionally graded porous plates are evaluated. The effectiveness of the proposed method is verified by comparing its numerical results with those of other methods reported in the relevant literature. The presented results show that the variable thickness, porosity parameter and material gradations have a significant effect on the mechanical responses of the plates. Decreasing the thickness and increasing the porosity due to reducing the stiffness of the plate decrease the buckling load and frequencies and increase the deformation of the plate. © 2022, The Author(s), under exclusive licence to Società Italiana di Fisica and Springer-Verlag GmbH Germany, part of Springer Nature.
Diamond and Related Materials (09259635) 121
Molecular dynamics (MD) simulations are used to investigate the tensile properties and fracture behavior of Hydrogen (H)- and Fluorine (F)-chemisorbed single-walled silicon carbide nanotubes (SWSiCNTs). Stress-strain curves are obtained and Young's modulus, toughness, tensile strength, as well as maximum strain of nanotubes are determined through stress-strain profiles. The results are compared to those of single-walled carbon nanotubes (SWCNTs) and a detailed analysis of the tensile fracture behavior of both nanotubes, i.e., SWSiCNTs and SWCNTs, is made. It is found that the functionalized nanotubes possess lower stress and strain at the breaking point than those of their pure counterparts (SWSiCNTs 0% and SWCNTs 0%). The increase of functionalization weight leads to reduced Young's modulus, toughness, and tensile strength. Concerning fluorination and hydrogenation, the fluorination of nanotubes has less influence on the weakening of Young's modulus in every functionalization degree when the findings of F-functionalized SWSiCNTs and SWCNTs (F-fSWSiCNTs and F-fSWCNTs) are compared to those of pure nanotubes. Fluorinated and hydrogenated armchair SWSiCNTs experience a nearly equal value of toughness in each weight of functionalization. Similar results are seen in the zigzag fSWSiCNTs which means that the absorption ability of strain energy in the zigzag H- and F-fSWSiCNTs is almost the same. As the weight of functionalization increases from the minimum value to the maximum one, the variation of ultimate stress with the degree of functionalization for the H-fSWCNTs and zigzag H-fSWSiCNT undergoes more reduction in comparison with their F-functionalized counterparts. Also, the armchair functionalized nanotubes are proved to be more capable of withstanding a larger fracture strain than that of their zigzag counterparts in each desired weight of functionalization. Regarding the fracture behavior of nanotubes, the rupture propagation tends to happen in a benzene ring that has at least three functional atoms and one of its grafts has been broken before. © 2021
Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science (20412983) 236(7)pp. 3663-3671
In this paper, an investigation into the thermal conductivity of cross-linked functionalized carbon nanotubes under physical adsorption of polyethylene (PE) chains (cfCNTs/PE) is performed using molecular dynamics (MD) simulations. To have a comprehensive study, the covalently attached functional groups with two types of distribution patterns, namely mapped and wrapped configurations, are used. The cfCNT/PE shows a smaller thermal conductivity than that of pure one. Also, the results demonstrate that the thermal conductivity of cfCNTs reduces by the physisorption of PE chains. By rising the weight percentage of physisorbed PE, the thermal conductivity of cfCNT/PE reduces more. Based on the results, for the constant weight percentage of non-covalent PE chains, the thermal conductivity increases as the number of cross-linked PE chains augments. © IMechE 2021.
Composites Part A: Applied Science and Manufacturing (1359835X) 152
Piezoresistivity and electrical conductivity of carbon nanotube (CNT)/graphene nanoplatelet (GNP)-filled polymer nanocomposites are investigated using a 3D Monte Carlo analytical-geometrical model. GNPs and CNTs are considered as randomly distributed solid thin rectangular cube and cylinder, respectively. After establishment of a random CNT/GNP network, electrical conductivity and relative resistance change with strain is calculated. Model considers effect of CNT and GNP deformation on filler separation distance as the dominant factor for percolation tunneling. Comparing model results with experimental data of hybrid nanocomposites showed a good agreement for electrical conductivity and piezoresitivity. Analytical model is developed on the basis of geometrical tunneling percolation theory to consider the effect of several parameters like height of barrier potential, GNP side length, CNT orientation and dimensions on electric behavior of nanocomposites. Results revealed that CNT dispersion state and GNP dimensions have significant effects on the percolation threshold and resistivity change ratio of nanocomposites with strain. © 2021 Elsevier Ltd
Ali, M.M.A. ,
Jamali a., A. ,
Asgharnia a., ,
Ansari, R. ,
Mallipeddi, R. Neural Computing And Applications (09410643) 34(2)pp. 1345-1357
In system control, stability is considered the most important factor as unstable system is impractical or dangerous to use. Lyapunov direct method, one of the most useful tools in the stability analysis of nonlinear systems, enables the design of a controller by determining the region of attraction (ROA). However, the two main challenges posed are—(1) it is hard to determine the scalar function referred to as Lyapunov function, and (2) the optimality of the designed controller is generally questionable. In this paper, multi-objective genetic programming (MOGP)-based framework is proposed to obtain both optimal Lyapunov and control functions at the same time. In other words, MOGP framework is employed to minimize several time-domain performances as well as the ROA radius to find the optimal Lyapunov and control functions. The proposed framework is tested in several nonlinear benchmark systems, and the control performance is compared with state-of-the-art algorithms. © 2021, The Author(s), under exclusive licence to Springer-Verlag London Ltd., part of Springer Nature.
International Journal for Numerical Methods in Engineering (00295981) 123(10)pp. 2309-2337
The integration of generalized differential quadrature techniques and finite element (FE) methods has been developed during the past decade for engineering problems within classical continuum theories. Hence, the main objective of the present study is to propose a novel numerical strategy called the multi-patch variational differential quadrature (VDQ) method to model the structural behavior of plate structures obeying the shear deformation plate theory within the strain gradient elasticity theory. The idea is to divide the two-dimensional solution domain of the plate model into sub-domains, called patches, and then to apply the VDQ method along with the FE mapping technique for each patch. The formulation is presented in a weak form and due to the (Formula presented.) -continuity requirements the corresponding compatibility conditions are applied through the patch interfaces. The Lagrange multiplier technique and the penalty method are implemented to apply the higher-order compatibility conditions and boundary conditions, respectively. To show the efficiency of the proposed method, numerical results are provided for plate structures with both regular and irregular solution domains. The provided numerical examples demonstrate the applicability and accuracy of the method in predicting the bending and vibration behavior of plate structures following the higher-order plate model. © 2022 The Authors. International Journal for Numerical Methods in Engineering published by John Wiley & Sons Ltd.
International Journal of Structural Stability and Dynamics (02194554) 22(6)
This paper uses the higher-order shear deformation theory (HOSDT) to analyze the nonlinear resonance of functionally graded graphene platelet-reinforced porous (FG-GPL-RP) circular cylindrical shell with geometrical imperfections subjected to the harmonic transverse loading. The shell considered is surrounded by the elastic Winkler-Pasternak foundation. Based on Hamilton's principle, the nonlinear governing equations of motion of the imperfect system considered are established using the first-order and various higher-order shear deformation shell theories that contain a unified higher-order displacement field. Four types of porosity and graphene nanoplatelet distribution patterns are considered. The modified Halpin-Tsai scheme and rule of mixture are utilized to calculate the effective properties of FG-GPL-RP materials. Explicit expressions of the nonlinear primary resonance of imperfect FG-GPL-RP cylindrical shells for simply-supported boundary conditions are achieved by the Galerkin technique and method of multiple scales. After verifying the accuracy of the model used and the results obtained, the influences of the geometric parameters, material properties and distribution and imperfection value on the nonlinear primary resonant response of the imperfect FG-GPL-RP circular cylindrical shells are examined in detail. © 2022 World Scientific Publishing Company.
Ansari, R. ,
Oskouie, M.F. ,
Nesarhosseini s., ,
Rouhi h., H. Transport In Porous Media (15731634) 142(1-2)pp. 63-87
In this paper, the geometrically nonlinear thermally induced vibration response of beams made of porous functionally graded materials (FGMs) under thermal shock is investigated using a novel numerical approach. The material properties are considered to be temperature- and position-dependent. It is also assumed that the beams are embedded in an elastic medium which is considered as Winkler–Pasternak type. Hamilton’s principle, the Timoshenko beam theory and the von Kármán geometrical nonlinear assumptions are used to derive the equations of motion. The matrix representation of relations is given that can be efficiently utilized in numerical approaches. Solution in time domain is done using the Newmark algorithm according to the constant average acceleration technique. In the space domain, the generalized differential quadrature and variational differential quadrature (VDQ) methods are employed for discretization. Using VDQ leads to compact/efficient vector–matrix relations which can be readily utilized in the coding process. The numerical results are presented to analyze the effects of power law index, boundary conditions, material porosity, elastic foundation and length-to-thickness ratio on the nonlinear thermally induced vibrations of FGM porous beams. It is shown that considering the even distribution, the vibration amplitude of beams decreases as the porosity volume fraction gets larger, while it increases for the uneven distribution. Moreover, the time required to reach the steady state of vibrations increases with increasing the power law index of FGM. © 2021, The Author(s), under exclusive licence to Springer Nature B.V.
Mechanics Based Design of Structures and Machines (15397742) 50(10)pp. 3491-3510
The main objective of this study is the phase-field (PF) vibration analysis of cracked functionally graded graphene platelets-reinforced composite (FG GPL-RC) plates considering stationary cracks. Mindlin’s plate model and phase-field approach are used to express the governing equations. The plate is numerically modeled using the variational finite difference (FD) method. Various convergence studies are provided to show the performance of the introduced numerical model. Different cracked patterns are regarded to investigate the linear vibration of cracked nanocomposite plates. The numerical results clearly demonstrate that the phase-field model can be effectively employed to simulate the vibration behavior of cracked nanocomposite plates. © 2020 Taylor & Francis Group, LLC.
Thin-Walled Structures (02638231) 181
In this article, a numerical approach is presented for the large deformation analysis of shell-type structures made of Neo-Hookean and Kirchhoff–St Venant materials within the framework of the seven-parameter shell theory. Work conjugate pair of the second Piola–Kirchhoff stress and Green–Lagrange strain tensors are taken for the macroscopic stress and strain measures in this total Lagrangian formulation. By defining displacement vector, deformation gradient and stress tensor in the Cartesian coordinate system, and using the chain rule for taking derivative of tensors, the complications of using the curvilinear coordinate system are bypassed. The variational differential quadrature (VDQ) technique as an effective numerical solution method is applied to obtain the weak form of governing equations. Being locking-free, simple implementation, computational efficiency and fast convergence rate are the main features of the proposed numerical approach. A number of well-known benchmark problems are solved in order to reveal the accuracy and efficiency of the method. It is shown that this approach is able to predict the large deformations of hyperelastic shell-type structures in an efficient way. © 2022 Elsevier Ltd
Journal of Molecular Graphics and Modelling (10933263) 111
The mechanical characteristics of reinforced polymer nanocomposites with Hydrogen (H)- and Fluorine (F)-functionalized silicon carbide nanotubes (H-and F-fSiCNTs) are investigated herein using molecular dynamics (MD) simulations. The effects of covalent functionalization and chirality of SiCNT, and diverse polymer materials on Young's modulus, maximum stress, and strain to the failure point, as well as strain energy are studied. The results reveal that by increasing the functionalization degree, the maximum stress, maximum strain, elastic modulus, and strain energy decrease. The tensile strength of polymer nanocomposites containing SiCNT is higher than that of pure polymer and polymers containing functionalized silicon carbide nanotubes (fSiCNTs). It is also found that the incorporation of fSiCNT into the polymer matrix (fSiCNT/polymer) gives rise to a considerable improvement in the ultimate strength of nanocomposites compared to the pure polymer. Polymer nanocomposites reinforced by armchair SiCNTs and fSiCNTs withstand higher maximum stresses and possess less longitudinal Young's modulus as compared to the same systems comprising zigzag nanotubes. In every percent of functionalization, the zigzag F-fSiCNT/polymer tends to have a higher Young's modulus as compared to the zigzag H-fSiCNT/polymer. Similarly, the armchair F-fSiCNTs incorporated into the polyethylene (PE) matrix (F-fSiCNTs/PE) are stiffer than the armchair H-fSiCNTs/PE in each weight of functionalization. Moreover, the armchair fSiCNTs/polymer nanocomposites show higher storage of strain energy in comparison with their zigzag counterparts. © 2021
International Journal of Applied Mechanics (17588251) 14(10)
In this paper, the incremental equilibrium equations and corresponding boundary conditions for the isotropic, hyperelastic and incompressible shells are derived and then employed in order to analyze the behavior of spherical and cylindrical shells subjected to external pressure. The generalized differential quadrature (GDQ) method is utilized to solve the eigenvalue problem that results from a linear bifurcation analysis. The results are in full agreement with the previously obtained results and the effects of thickness and mode number are studied on the shell's stability. For the spherical and cylindrical shells of arbitrary thickness which are subjected to external hydrostatic pressure, the symmetrical buckling takes place at a value of α1 which depends on the geometric parameter A1/A2 and the mode number n, where A1 and A2 are the undeformed inner and outer radii, respectively, and α1 is the ratio of the deformed inner radius to the undeformed inner radius. © 2022 World Scientific Publishing Europe Ltd.
Journal of Physics and Chemistry of Solids (00223697) 161
A two-step analytical model based on a percolation network model and electron tunneling theory has been developed to predict the electrical resistivity and percolation threshold of a hybrid nanocomposite system comprising carbon black (CB) and carbon nanotube (CNT). The nanostructure of a tunneling network consisting of CNT and CB agglomerates has been generated to study the effects of various parameters on electrical conductivity. Electron tunneling is the primary mechanism for electrical percolation, which is incorporated into the model by considering the effective tunneling distance of CNTs. Later, a percolation network model is introduced to evaluate the electrical properties of the hybrid nanocomposite. Our results indicate that a high level of alignment leads to a significant decrease of the percolation threshold with an increase in conductivity, while a low CB volume fraction with low intrinsic electrical conductivity degrades the percolation and overall conductivity. Our results also reveal that the addition of CB as a second filler in a hybrid nanocomposite leads to improvements in conductance and percolation threshold. Analytical results show that the current model agrees well with existing experimental data, which reveals that tunneling and percolation are the dominant mechanisms for transition behavior in electrical conductivity. © 2021 Elsevier Ltd
Sensors and Actuators A: Physical (09244247) 336
A novel one-step Monte-Carlo approach considering the orientation effect of carbon nanotubes (CNTs) in synergism with uniformly distributed ellipsoidal graphene nanoplatelets (GNPs) teamed up with percolation model is developed to study the percolation probability and gauge factor of hybrid CNT-GNP piezoresistive conductive network composite. A representative volume element is generated based on the randomly oriented rod-like CNTs and uniformly distributed disk-shape GNPs to examine the piezoresistive sensitivity developed by strain under tension. The model predictions are compared with experimental studies related to electrical conductivity and piezoresistivity of hybrid CNT-GNP nanocomposites and a good agreement is achieved. A parametric investigation of the influences of CNT volume fraction, degree of orientation, GNP diameter and volume fraction is performed on the piezoresistive sensitivity of nanocomposite. High piezoresistive sensitivity is achieved for scattered short aligned CNTs distributed in the matrix with sparse low aspect ratio GNPs. The results also demonstrated that high percolation probability is achievable for nanocomposite with longer CNTs oriented in random directions and perfect dispersion of GNPs with higher surface area. © 2022 Elsevier B.V.
Gholami y., Y. ,
Ansari, R. ,
Gholami, R. ,
Sadeghi f., F. Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science (20412983) 236(14)pp. 8116-8133
In this paper, a size-dependent nanoplate model is developed to describe the free vibration and buckling behaviors of magneto-electro-thermo-elastic (METE) rectangular nanoplates. It is assumed that the METE nanoplate is subjected to external electric voltage, external magnetic potential, and uniform temperature rise. The nonlocal elasticity theory along with the third-order shear deformation plate theory is employed for the size-dependent mathematical modeling of nanoplates. The presented model has two advantages over available models: (1) the need for the correction factor is bypassed and (2) it can be successfully applied to thick nanoplates. The governing equations and the corresponding boundary conditions are derived using the Hamilton’s principle which are then discretized on the space domain based on the generalized differential quadrature (GDQ) method. Afterward, an efficient numerical Galerkin procedure is adopted to reduce the discretized equations into Duffing-type ordinary differential equations. Numerical results are presented to examine the influences of nonlocal parameter, length-to-thickness ratio, temperature rise, external electric potential, external magnetic potential and type of boundary condition on the free vibration, and buckling behaviors of METE nanoplates. It is revealed that frequency and critical buckling load of nanoplates are dependent on magneto-electro-mechanical loadings, whereas they are less dependent on thermal loading. © IMechE 2022.
Ansari, R. ,
Hassani r., R. ,
Hasrati, E. ,
Rouhi h., H. JVC/Journal of Vibration and Control (10775463) 28(21-22)pp. 3019-3041
In this article, the vibrational behavior of conical panels in the nonlinear regime made of functionally graded graphene platelet–reinforced composite having a hole with various shapes is investigated in the context of higher-order shear deformation theory. To achieve this aim, a numerical approach is used based on the variational differential quadrature and finite element methods. The geometrical nonlinearity is captured using the von Karman hypothesis. Also, the modified Halpin–Tsai model and rule of mixture are applied to calculate the material properties of graphene platelet–reinforced composite for various functionally graded distribution patterns of graphene platelets. The governing equations are derived by a variational approach and represented in matrix-vector form for the computational purposes. Moreover, attributable to using higher-order shear deformation theory, a mixed formulation approach is presented to consider the continuity of first-order derivatives on the common boundaries of elements. In the numerical results, the nonlinear free vibration behaviors of functionally graded graphene platelet–reinforced composite conical panels including square/circular/elliptical hole and with crack are studied. The effects of boundary conditions, graphene platelet reinforcement, and other important parameters on the vibrational response of panels are comprehensively analyzed. © The Author(s) 2021.
Waves in Random and Complex Media (discontinued) (17455049) 32(6)pp. 2796-2811
A novel numerical approach is proposed herein to study thermomechanical wave propagation in annular disks made of viscoelastic materials under inner thermal shock based on the Lord–Shulman (L–S) theory and the Kelvin–Voigt model. It is assumed that the temperature change is considerable in comparison with the reference temperature and the original nonlinear form of energy equation is considered accordingly. In the polar coordinate system, the coupled governing equations are obtained in a weak form which is then solved using the variational differential quadrature (VDQ) technique. The influences of viscoelastic character and thermal shock on the propagation of temperature and radial displacement of disk are investigated. In addition, the predictions of thermally linear and nonlinear models are compared. © 2020 Informa UK Limited, trading as Taylor & Francis Group.
Engineering Computations (02644401) 39(5)pp. 1922-1946
Purpose: The paper aims to presents a numerical analysis of free vibration of micromorphic structures subjected to various boundary conditions. Design/methodology/approach: To accomplish this objective, first, a two-dimensional (2D) micromorphic formulation is presented and the matrix representation of this formulation is given. Then, two size-dependent quadrilateral and triangular elements are developed within the commercial finite element software ABAQUS. User element subroutine (UEL) is used to implement the micromorphic elements. These non-classical elements are capable of capturing the micro-structure effects by considering the micro-motion of materials. The effects of the side length-to-length scale parameter ratio and boundary conditions on the vibration behavior of 2D micro-structures are discussed in detail. The reliability of the present finite element method (FEM) is confirmed by the convergence studies and the obtained results are validated with the results available in the literature. Also, the results of micromorphic theory (MMT) are compared with those of micropolar and classical elasticity theories. Findings: The study found that the size effect becomes very significant when the side length of micro-structures is close to the length scale parameter. Originality/value: The study is to analyze the free vibrations of 2D micro-structures based on MMT; to develop a 2D formulation for micromorphic continua within ABAQUS; to propose quadrilateral and triangular micromorphic elements using UEL and to investigate size effects on the vibrational behavior of micro-structures with various geometries. © 2021, Emerald Publishing Limited.
Acta Mechanica (16196937) 233(9)pp. 3663-3677
Based on the micromorphic theory (MMT), the vibrational behavior of annular sector plates with different angles and subjected to various boundary conditions (BCs) is studied. To this end, the linear formulation of three-dimensional (3D) MMT is first presented and the matrix representation of this formulation is given. Then, a 3D size-dependent 8-node brick element is developed by the user element (UEL) subroutine within the commercial finite element software Abaqus to investigate the effects of microstructures on the vibration response of micromorphic structures. The effects of thickness-to-length scale parameter ratio and sector angle on the vibration behavior of the micromorphic annular sector plates are studied. Also, the results obtained by MMT are compared to those of the classical elasticity theory. © 2022, The Author(s), under exclusive licence to Springer-Verlag GmbH Austria, part of Springer Nature.
Ansari, R. ,
Oskouie, M.F. ,
Nesarhosseini s., ,
Rouhi h., H. Journal Of The Brazilian Society Of Mechanical Sciences And Engineering (16785878) 44(2)
In this work, a numerical study is presented for the free vibration behavior of piezoelectric Bernoulli–Euler nanoscale beams considering flexoelectric and nonlocal effects. Strain-driven nonlocal formulations of Eringen’s theory in both differential and integral forms are used to capture nonlocal influences. By Hamilton’s principle, the equation of motion and boundary conditions are obtained which are numerically solved. In the solution method, the finite difference and generalized differential quadrature (GDQ) methods are applied for discretizing the differential and integral equations, respectively. Also, matrix differential and integral operators are proposed. After investigating the convergence and validation of the approach, the influences of nonlocality, flexoelectric coefficient and slenderness ratio on the linear free vibrations of nanobeams subject to different end conditions are studied in the numerical results. It is revealed that the paradox related to the results of differential formulation for nanocantilevers is resolved by the proposed integral formulation. © 2022, The Author(s), under exclusive licence to The Brazilian Society of Mechanical Sciences and Engineering.
Arabian Journal for Science and Engineering (21914281) 46(8)pp. 7143-7151
The influence of agglomeration of SiC nanoparticles on the bulk thermal conducting behavior of aluminum (Al)-based nanocomposites is examined using a micromechanics-based hierarchical technique. The interfacial thermal resistance (ITR) between the ceramic nano-scale particles and the metallic matrix is included in the analysis. The predictions of the micromechanical model considering the agglomeration and ITR are in very good agreement with the available experimental results. The agglomeration of ceramic nanoparticles greatly reduces the thermal conducting coefficient of the Al-based nanocomposites. When the nanoparticle volume fraction is 10%, the thermal conductivity decreases from 132 to 115 W/mK with the formation of nanoparticle agglomeration. The uniform distribution of nanoparticles and the elimination of ITR can lead to a substantial enhancement in the nanocomposite thermal conductivity. When the volume fraction is 10%, the thermal conductivity increases from 115 to 188 W/mK by uniform dispersing the nanoparticles and removing the SiC/Al ITR. Moreover, the effects of amount, and diameter of nano-scale particles as well as the constituent material properties on the bulk thermal conductivity of the SiC nanoparticle-filled Al nanocomposites are examined. When the SiC diameter increases from 35 nm to 3.5 µm, the thermal conductivity of the Al-based composite increases from 132 to 173 W/mK. © 2021, King Fahd University of Petroleum & Minerals.
Ansari, R. ,
Hassani r., R. ,
Hasrati, E. ,
Rouhi h., H. European Physical Journal Plus (21905444) 136(6)
Presented herein is a novel numerical approach for the vibrational analysis of conical panels with arbitrary-shaped holes made of functionally graded graphene platelet-reinforced composite (FG-GPLRC) within the framework of higher-order shear deformation theory (HSDT). The developed approach can be called variational differential quadrature finite element method (VDQFEM) as it is based on the ideas of VDQ and finite element methods. The governing equations are obtained by means of Hamilton’s principle. Also, the relations of paper are presented in a new matrix–vector form which can be efficiently utilized in the coding process of numerical techniques. By VDQFEM, the space domain of structure is first transformed into a number of finite elements. Then, the VDQ discretization technique is implemented within each element to derive the mass and stiffness matrices. Finally, the assemblage procedure is followed for obtaining total mass and stiffness matrices. Due to using HSDT, a novel mixed formulation approach is also proposed to accommodate the continuity of first-order derivatives on the common boundaries of elements. Conical panels with square/circular/elliptical cutout and with crack are selected to generate the numerical results. In the numerical examples, the effects of geometrical properties and reinforcement with GPL on the resonant frequencies of panels subject to various boundary conditions are investigated. © 2021, The Author(s), under exclusive licence to Società Italiana di Fisica and Springer-Verlag GmbH Germany, part of Springer Nature.
Ansari, R. ,
Hassani r., R. ,
Gholami y., Y. ,
Rouhi h., H. European Physical Journal Plus (21905444) 136(7)
Based on the ideas of variational differential quadrature (VDQ) method and position transformation, an efficient numerical variational strategy is proposed in this paper to analyze the large deformations of hyperelastic structures in the context of three-dimensional (3D) compressible and incompressible nonlinear elasticity theories. Based on the minimum total potential energy principle together with the Neo-Hookean model, the governing equations are derived. The relations of paper are presented in novel vector–matrix format. Replacing the tensor form of formulations with matricized ones is a novelty of present work since the matricized formulations can be readily employed for the programming in numerical approaches. Discretizing is also carried out via VDQ operators. For applying the VDQ technique, the irregular domain of elements is transformed into a regular one by the method of mapping of position field based on the finite element shape functions. This feature enables the proposed VDQ-transformed approach to solve problems with irregular domains. Moreover, the developed formulation is simple, compact and easy to implement. Considering structures with various shapes, several illustrative convergence and comparative investigations are given to assess the performance of the approach in both compressible and incompressible regimes. Good accuracy and computational efficiency can be reported as the features of developed VDQ-based approach. © 2021, The Author(s), under exclusive licence to Società Italiana di Fisica and Springer-Verlag GmbH Germany, part of Springer Nature.
Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science (20412983) 235(21)pp. 5709-5717
This paper is intended to study the dynamic oscillatory behavior of chloride ion inside electrically charged open carbon nanocones (CNCs) using the molecular dynamics (MD) simulations. The small and wide ends of nanocone are assumed to be identically and uniformly charged with positive electric charges. In the simulation, the Tersoff-Brenner (TB) and the Lennard-Jones (LJ) potential functions are employed to evaluate the interatomic interactions between carbon atoms and the van der Waals (vdW) interactions between the ion and the nanocone, respectively. The Coulomb potential is also adopted to evaluate the electrostatic interactions between the ion and the electric charges distributed at both ends of nanocone. Numerical results are presented to examine the effects of magnitude of electric charges, initial separation distance and initial velocity on the mechanical oscillatory behavior of system and the obtained results are also compared with the ones related to an uncharged nanocone. It is found that operating frequency as well as escape velocity enhance considerably as a result of electrostatic interactions. It is further found that regardless of the value of electric charges, optimal oscillation frequency is achievable when no initial velocity is imposed on the ion initially located inside of nanocone with an offset of 2 Å from its small end. © IMechE 2021.
Journal Of Molecular Modeling (16102940) 27(12)
The mechanical properties of oxygen-functionalized single-walled carbon nanotubes (CNTs) are studied herein by molecular dynamics (MD) simulations. An analysis of the random distribution of oxygen atoms on CNTs of various functionalization percentages is presented in this study. The influences of the nanotube length, diameter, and the percentage of functionalization on longitudinal Young’s modulus, failure stress, strain, and toughness are investigated. The results show that for both zigzag and armchair chiralities, Young’s modulus decreases by increasing the nanotube diameter and length-to-diameter ratio. Also, the values of all studied properties including Young’s modulus, stress, strain, and toughness are reduced by increasing the functionalization percentage until the nanotube reaches failure. Moreover, the reason for the alteration of the mechanical properties of nanotubes and the behavior of the stress-strain diagram are discussed. © 2021, The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.
Pouyanmehr, R. ,
Pakseresht m., M. ,
Ansari, R. ,
Hassanzadeh-aghdam, M.K. Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science (20412983) 235(24)pp. 7785-7799
One of the limiting factors in the life of lithium-ion batteries is the diffusion-induced stresses on their electrodes that cause cracking and consequently, failure. Therefore, improving the structure of these electrodes to be able to withstand these stresses is one of the ways that can extend the life of the batteries as well as improve their safety. In this study, the effects of adding graphene nanoplatelets and microparticles into the active plate and current collectors, respectively, on the diffusion induced stresses in both layered and bilayered electrodes are numerically investigated. The micromechanical models are employed to predict the mechanical properties of both graphene nanoplatelet-reinforced Sn-based nanocomposite active plate and silica microparticle-reinforced copper composite current collector. The effect of particle size and volume fraction in the current collector on diffusion induced stresses has been studied. The results show that in electrodes with a higher volume fraction of particles and smaller particle radii, decreased diffusion induced stresses in both the active plate and the current collector are observed. These additions will also result in a significant decrease in the bending of the electrode. © IMechE 2021.
Proceedings of the Institution of Mechanical Engineers, Part L: Journal of Materials: Design and Applications (20413076) 235(12)pp. 2762-2770
In this article, we study the thermal conductivity coefficient of the polypropylene composite reinforced by graphene sheets. A hierarchical approach is used for the investigation, which is started by molecular dynamics simulation to evaluate the thermal conductivity coefficient of graphene sheets and continued by the finite element analysis to evaluate the thermal conductivity coefficient of graphene reinforced polypropylene at different temperatures. It is shown that inclusion of the graphene sheets can lead to increasing the thermal conductivity coefficient of the polypropylene, especially when the nanosheets are directed along the temperature difference. Moreover, the higher volume percentages of the graphene sheets in the polymer matrix enhance the thermal conductivity. © IMechE 2021.
Ansari, R. ,
Oskouie, M.F. ,
Nesarhosseini s., ,
Rouhi h., H. Applied Physics A: Materials Science and Processing (14320630) 127(7)
A numerical investigation is performed to examine the static bending behavior of piezoelectric nanoscale beams subjected to electrical loading, considering flexoelectricity effects and different kinematic boundary conditions. The nanobeams are modeled by the Bernoulli–Euler beam theory, and the stress-driven integral nonlocal model is used in order to capture size influences. It is also considered that the nanobeams are embedded in an elastic medium. The Winkler and Pasternak elastic foundation models are used for simulating the substrate medium. Based upon Hamilton’s principle and the electrical Gibbs free energy, the governing equations are derived which are then numerically solved via a finite difference-based method. Numerical results are presented to study the influences of nonlocal, flexoelectric and Winkler/Pasternak parameters on the bending response of piezoelectric nanobeams under various end conditions. © 2021, The Author(s), under exclusive licence to Springer-Verlag GmbH, DE part of Springer Nature.
Applied Mathematical Modelling (0307904X) 100pp. 689-727
Introduced in this paper is the complete nonlinear model of the micropolar theory (MPT) for shell-type materials. Considering the three-dimensional kinematic model in a convected curvilinear coordinate system, the Lagrangian description of micromorphic theory (MMT) is formulated first. Due to certain assumptions, i.e. skew-symmetricity of micro-displacement and orthogonality of micro-deformation tensors, the highly nonlinear micropolar continuum theory is obtained. Unlike the conventional knowledge in the literature, it is found that not only MPT is not a simple version of MMT but also the present micropolar formulation can be reduced to the corresponding micromorphic shell elasticity. Also, unlike the Kafadar-Eringen's nonlinear micropolar model which only predicts the large micro-deformations, the developed micropolar theory is able to investigate the physical behavior in case of large elastic macro-deformations, for the first time. The isogeometric analysis (IGA) solution method with standard base functions is used to prevent the locking issues arising in the low-order finite element analysis (FEA) of thin shells. Accordingly, the proposed IGA micropolar shell model possesses 10-DOFs (degrees of freedom) standing for 7 macro-displacements and 3 micro-rotations. Size / inhomogeneity effects of small-scale / micropolar materials are investigated in the benchmark problems of geometrically nonlinear shells. As a result, it is revealed that the paper contributes to literature by developing the nonlinear micropolar shell theory which is able of capturing large macro- and micro-deformations. © 2021 Elsevier Inc.
Ajori, S. ,
Haghighi s., ,
Parsapour h., ,
Ansari, R. Journal Of Molecular Modeling (16102940) 27(11)
The endohedral functionalization of carbon nanotubes (CNTs) with nanowires (NWs), i.e., NWs@CNTs, has been the center of attention in a lot of research due to the applications of NWs@CNTs in nanoelectronic devices, heterogeneous catalysis, and electromagnetic wave absorption. To this end, based on the classical molecular dynamics (MD) simulations, the effect of four pentagonal structures of encapsulated metallic nanowires (mNWs), namely the eclipsed pentagon (E), the deformed staggered pentagon (Ds), staggered pentagon (S), and staggered pentagonal structure without the monatomic chain passing through the centers of the parallel pentagons (R) configurations on the vibrational behavior of CNTs, is investigated. Also, the effects of geometrical parameters such as length and radius of CNTs on the natural frequencies of simulated models are explored. The results illustrate that by increasing the length, the natural frequency of pure CNTs and mNWs@CNTs decreases. In a similar length, mNWs@CNTs possess lower natural frequencies compared to the pure CNTs. According to the results, the highest and lowest natural frequencies are calculated by inserting the S structure of sodium NW and Ds structure of aluminum NW inside their proper armchair CNT, i.e., Na-S NW@ (9,9) CNT and Al-Ds NW@ (7,7) CNT, respectively. © 2021, The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.
Ansari, R. ,
Hassani r., R. ,
Hasrati, E. ,
Rouhi h., H. Acta Mechanica (16196937) 232(9)pp. 3417-3439
Based on Reddy’s third-order shear deformation theory and mixed formulation, a new numerical approach in the variational framework is developed to analyze the geometrically nonlinear free vibration behavior of cylindrical panels having cutouts with various shapes (e.g., square, circular, elliptical) under arbitrary boundary conditions. It is also assumed that the panel is made of functionally graded graphene platelet-reinforced composite with various patterns for the distribution of GPLs along the thickness direction whose effective properties are estimated using the modified Halpin–Tsai model in conjunction with the rule of mixture. The proposed approach can be named VDQFEM as it utilizes the VDQ and FE methods. Efficient matrix formulation, being free from the locking problem, computational efficiency and being able to solve problems with concave and polygon domains are the main features of VDQFEM. Selected numerical results are given to investigate the influences of geometrical parameters and weight fraction/distribution pattern of GPLs on the large-amplitude vibration response of panels with various cutouts and boundary conditions. © 2021, The Author(s), under exclusive licence to Springer-Verlag GmbH Austria, part of Springer Nature.
Proceedings of the Institution of Mechanical Engineers, Part L: Journal of Materials: Design and Applications (20413076) 235(8)pp. 1925-1936
A multiscale approach is used here to investigate the impact properties of carbon fibre/carbon nanotube-reinforced polymer. For this purpose, the mechanical properties of the carbon nanotubes (CNTs) are obtained by molecular dynamics simulations. Then, they are included in the polyethene matrix, and the mechanical properties of CNT-reinforced polyethene are computed using a stochastic approach. Considering the CNT-reinforced polyethene as the matrix, the effect of adding the carbon fibres on its mechanical properties is investigated in the next step. Finally, utilizing a stochastic method, the macro-scale mechanical properties of carbon fibre/carbon nanotube-reinforced polymer are computed. Thereafter, the impact test is applied on the models. The finite element method is used to investigate the mechanical and impact properties of representative volume elements. The effects of waviness, volume percentage and aspect ratio of the carbon fibre and CNT on the mechanical properties of the multiscale composite are evaluated. It is shown that reinforcing the polyethene matrix by carbon fibres and CNTs significantly increases its impact resistance. Adding 3% and 5% volume percentages of CNT into 3%-carbon fibre/polyethene and 5%-carbon fibre/polyethene respectively, resulted in 26% and 47% improvement in the impact resistance of the composite. © IMechE 2021.
Materials Science and Engineering: B (09215107) 271
In this paper, antimonene nanosheets are simulated using finite element modeling. First, the elastic properties of antinomene are obtained using the density functional theory as well as the element properties, which are used to represent Sb-Sb bonds in the structure of antimonene. Then, developed model is used to calculate Young's modulus, critical compressive force and fundamental frequency of the antinomene nanosheet with different geometrical parameters. It is shown that proposed simulation can predict Young's modulus of monolayer antinomene accurately. Also, it is revealed that increasing the horizontal side length increases the stiffness of nanosheet, while increasing the vertical side length has the opposite result. Moreover, critical compressive force of nanosheet increases by increasing vertical side length, whereas increasing the horizontal side length leads to the opposite result. Furthermore, vibrational frequency of the antimonene significantly decreases by increasing horizontal side length, while changes observed by increasing vertical side length are negligible. © 2021 Elsevier B.V.
International Journal of Non-Linear Mechanics (00207462) 135
Studying the large-amplitude forced vibration characteristics of micropolar shell-type structures is the main objective of this paper. In order to obtain the full geometrically nonlinear model of micropolar theory, the micromorphic seven-parameter shell kinematic is first developed. Via a nonlinear micro-motion map, the extracted formulation is fitted for the micropolar continuum. As a result, possessing three stress–strain fields with eighteen independent elastic parameters of a linear material, the proposed micropolar shell theory is able to capture the inhomogeneity and size-effects. On the basis of Hamilton's principle, the variational form of governing equations of motion is determined. The finite element isogeometric solution approach is then utilized to produce the geometry and approximate the displacement field in mid-surface area of shell. This would be helpful for resolving the locking and instability issues of the traditional low-order standard finite element shell models. By discretizing the period of harmonic vibration, a numerical method is also implemented in time domain. To demonstrate the microstructural effects, dynamic behavior of micropolar plate- and shell-type structures are investigated in several parametric studies. Since the classical strain and stress tensors are retained in present micropolar elasticity, both the large macro- and micro-deformations are captured for the first time. © 2021 Elsevier Ltd
Ansari, R. ,
Hassani r., R. ,
Oskouie, M.F. ,
Rouhi h., H. Engineering with Computers (14355663) 37(4)pp. 3251-3263
In this article, a new solution approach is developed to numerically compute large deformations of 3D hyperelastic solids based on the compressible nonlinear elasticity. The governing equations are derived by the minimum total potential energy principle, and the Neo-Hookean model is used for the hyperelastic character of material. One of the key novelties of the work is its formulation in which the tensor form of equations is replaced by an efficient matrix–vector form that can be readily utilized in the coding process. Moreover, the variational differential quadrature technique is adopted to arrive at the discretized governing equations in a direct way. Simple implementation, fast convergence rate, and computational efficiency are the main advantages of present approach. Through some examples, the accuracy and effectiveness of the proposed numerical approach are revealed. © 2020, Springer-Verlag London Ltd., part of Springer Nature.
Journal Of Molecular Modeling (16102940) 27(6)
In this article, the density functional theory is applied to characterize the mechanical properties of single-walled nanotubes of group IV of the periodic table. These materials include carbon nanotube, silicon nanotube, germanium nanotube, and stanene nanotube. (10,10) armchair nanotube is selected for the investigation. By establishing a link between potential energy expressions in molecular and structural mechanics, a finite element approach is proposed for modeling nanotubes. In the proposed model, the nanotubes are considered as an assemblage of beam elements. Young’s modulus of the nanotubes is computed by the proposed finite element model. Young’s modulus of carbon, silicon, germanium, and tin nanotubes are obtained as 1029, 159.82, 83.23, and 83.15 GPa, respectively, using the density functional theory. Also, the finite element approach gives the values as 1090, 154.67, 85.2, and 82.6 GPa, respectively. It is shown that the finite element model can predict the results of the density functional theory with good accuracy. © 2021, The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.
Physica B: Condensed Matter (09214526) 610
In this paper, a molecular dynamics approach is used to characterize the mechanical characteristics of oxygen-functionalized single-walled silicon carbide nanotubes. The influences of different parameters including the nanotube length, diameter and functionalization percentage on the mechanical properties of the oxygen-functionalized nanotubes are investigated. The evaluated mechanical properties include elastic modulus, maximum stress, maximum strain and the value of toughness. It is seen that increasing the diameter and length-to-diameter ratio leads to decrease in the modulus of elasticity of zigzag and armchair nanotubes. Besides, Young's modulus, maximum stress, maximum strain and toughness of armchair and zigzag oxygen-functionalized silicon carbide nanotubes decrease by increasing the functionalization percentage. In the last step, the effect of functionalization pattern on the mechanical properties is studied. © 2021
Iranian Journal Of Materials Science And Engineering (17350808) 18(2)
Phenomenological methods are more diagnostic tools than a predictor, so multi-crystalline material approaches based on their microstructures have been proposed during the last years. The purpose of this research is to review methods taking into account the effect of microstructures and texture deformation on predicting the behavior of sheet metals. These methods can be categorized into six general groups: Taylor-type models, crystal plasticity finite element methods, strain gradient methods, methods that consider dislocations, self-consistent methods, methods based on fast Fourier transform. This paper attempts to explain and compare these methods that have been used to forecasting forming limits or stress-strain curves. © 2021, Iran University of Science and Technology. All rights reserved.
Ansari, R. ,
Oskouie, M.F. ,
Roghani m., ,
Rouhi h., H. Acta Mechanica (16196937) 232(6)pp. 2183-2199
In this paper, a nonlinear formulation for beam-type structures is presented within the framework of two-phase stress-driven (SD) nonlocal theory. Various boundary conditions are considered for the beams, and it is assumed that they are on the Winkler- and Pasternak-type elastic foundations. It is considered that the beams are made of laminated functionally graded-graphene platelet-reinforced composite (FG-GPLRC) whose properties are estimated by means of the Halpin–Tsai model. The Euler–Bernoulli beam theory is also used for the modeling. The governing equations are derived based on the integral form of SD nonlocal theory using a variational approach considering geometrical nonlinearity. The equations of the SD model in differential form in conjunction with associated constitutive boundary conditions are also obtained. Moreover, a numerical approach based upon the generalized differential quadrature (GDQ) method is developed for the solution of the nonlinear bending problem. The influences of volume fraction/distribution pattern of GPLs, nonlocality, elastic foundation, and geometrical parameters on the bending response of beams under different end conditions are investigated. Furthermore, comparisons are given between the linear and nonlinear results. © 2021, The Author(s), under exclusive licence to Springer-Verlag GmbH, AT part of Springer Nature.
Hosseini s.m.j., ,
Ansari, R. ,
Torabi, J. ,
Hosseini, K. ,
Zabihi, A. Iranian Journal Of Science And Technology, Transactions Of Mechanical Engineering (22286187) 45(4)pp. 891-909
The main objective of this investigation is to study the size-dependent dynamic pull-in instability of nanobeams based on the nonlocal strain gradient theory (NLSGT) and Euler–Bernoulli beam model. To this end, the partial differential equation is obtained based on the NLSGT considering the electrostatic, fringing field, and intermolecular nonlinear forces. Then, the Galerkin method and the homotopy analysis method (HAM) were employed to solve the nonlinear governing equation. To validate the proposed results, the non-dimensional natural frequency and pull-in voltage are compared with the previously published results. Likewise, the analytical results of the HAM are compared with those obtained based on the Runge–Kutta numerical method. Besides, the impacts of the NLSGT, strain gradient theory, nonlocal theory, and classical theory on the dynamic behavior of nanobeams are investigated in the same situation. The pull-in voltage is also presented and the effects of electrostatic forces, fringing field, and initial gap are discussed in detail for different boundary conditions. © 2020, Shiraz University.
Mechanics of Materials (01676636) 157
In this article, the effect of adding nanotubes made by elements from group IV of the periodic table with different lengths and volume fractions on the axial elastic modulus of the epoxy matrix is investigated. For this purpose, carbon, silicon, germanium, and tin nanotubes (CNT, SiNT, GeNT and SnNT) are considered as reinforcement. At the nanoscale, the axial Young's modulus is obtained using a finite element method (FEM) based on the molecular structural model in which the beam and solid continuum are used for embedded nanotubes (NTs) and matrix, respectively. It is shown that CNT has the most significant effect on strengthening the epoxy matrix. For example, at a 5% CNT volume fraction with a length of 300Å, the axial elastic moduli of CNT, SiNT, GeNT, and SnNT/epoxy increase by 1.58%, 1.37%, 1.34%, and 1.32%, respectively. © 2021 Elsevier Ltd
Thin-Walled Structures (02638231) 167
The micropolar continuum theory (MPT) is able to describe the influence of micro-structures on the mechanical behavior of materials where the classical theories of elasticity are unable to interpret. In this paper, the free vibration analysis of three-dimensional (3D) micropolar structures with different geometries is presented. To this aim, first, based on the 3D linear elasticity, MPT is formulated. Then a novel size-dependent quadratic tetrahedral element is developed by the user element subroutine (UEL) within commercial finite element software ABAQUS to study the free vibration behavior of micropolar structures with various geometries. The length scale parameter effects on the dimensionless natural frequencies of micropolar structures with various geometries are studied. © 2021 Elsevier Ltd
Ansari, R. ,
Nesarhosseini s., ,
Oskouie, M.F. ,
Rouhi h., H. European Physical Journal Plus (21905444) 136(8)
Presented herein is a size-dependent Bernoulli–Euler beam model for the buckling analysis of piezoelectric nanobeams under electrical loading with the consideration of flexoelectricity influence. In order to capture size effects, the stress-driven model of nonlocal theory is utilized. Moreover, it is considered that the nanobeams are embedded in an elastic medium. According to a variational approach, the governing equations including nonlocal and flexoelectricity effects are obtained. Also, using the generalized differential quadrature technique, a numerical solution approach is proposed for calculating buckling loads of piezoelectric nanobeams with different boundary conditions. The effects of flexoelectricity, nanoscale and elastic foundation on the buckling behavior of nanobeams are studied through presenting some numerical examples. © 2021, The Author(s), under exclusive licence to Società Italiana di Fisica and Springer-Verlag GmbH Germany, part of Springer Nature.
European Physical Journal Plus (21905444) 136(7)
A physics-based hierarchical modeling approach considering tunneling resistance through polymer is proposed to predict the percolation threshold and resistivity of carbon nanotube (CNT)/graphene nanoplatelet (GNP)-reinforced polymer hybrid nanocomposites. At first, a method is developed to calculate the resistivity of CNT-polymer nanocomposites. Then, percolation theory model is employed to calculate the percolation threshold of CNT-reinforced nanocomposites. At the end, an analytical model is presented for estimating the resistivity of CNT/GNP hybrid nanocomposites. The effects of barrier height, nanofiller aspect ratio and tunneling distance on the percolation threshold and resistivity of hybrid nanocomposites are extensively investigated. The results show that the percolation threshold depends on many factors such as aspect ratio, electrical conductivity and volume fraction of nanofillers. It is clearly shown that the smaller GNP aspect ratio leads to an increase in percolation threshold and electrical resistivity. The results also indicate the dominant role of nanofiller volume fraction at low tunneling distance. The model results are compared with experimental data in the literature for GNP/CNT hybrid nanocomposites where it is demonstrated that the represented model is able to explain the impact of electrical tunneling on the resistivity of polymer nanocomposites. © 2021, The Author(s), under exclusive licence to Società Italiana di Fisica and Springer-Verlag GmbH Germany, part of Springer Nature.
Bulletin of Materials Science (02504707) 44(1)
This study focuses on the van der Waals (vdW) interactions and oscillatory behaviour of nested spherical fullerenes (carbon onions) in the vicinity of a single-layer graphene (SLG) sheet. The carbon onions are of Ih symmetries and the graphene sheet is modelled as a fully constrained flat surface. Employing the continuum approximation along with the 6–12 Lennard-Jones (LJ) potential function, explicit analytical expressions are determined to calculate the vdW potential energy and interaction force. The equation of motion is solved numerically based on the actual force distribution to attain the displacement and velocity of the carbon onion. Using the conservation of mechanical energy principle, a semi-analytical expression is also derived to accurately evaluate the oscillation frequency. Numerical results are presented to examine the influences of size of carbon onion and initial conditions (initial separation distance and initial velocity) on the operating frequency of carbon onion–SLG sheet oscillators. It is shown that carbon onion executes oscillatory motion above the graphene sheet with frequencies in the gigahertz (GHz) range. It is further observed that smaller structures of carbon onions produce greater frequencies. We comment that the presented results in this study would contribute to the development of new generation of nano-oscillators. © 2021, Indian Academy of Sciences.
Kohansal vajargah, M. ,
Ansari, R. ,
Oskouie, M.F. ,
Bazdid-vahdati m., Applied Mathematics and Mechanics (English Edition) (02534827) 42(7)pp. 999-1012
Based on the micropolar theory (MPT), a two-dimensional (2D) element is proposed to describe the free vibration response of structures. In the context of the MPT, a 2D formulation is developed within the ABAQUS finite element software. The user-defined element (UEL) subroutine is used to implement a micropolar element. The micropolar effects on the vibration behavior of 2D structures with arbitrary shapes are studied. The effect of micro-inertia becomes dominant, and by considering the micropolar effects, the frequencies decrease. Also, there is a considerable discrepancy between the predicted micropolar and classical frequencies at small scales, and this difference decreases when the side length-to-length scale ratio becomes large. © 2021, Shanghai University.
International Journal of Innovation Management (13639196) (3)
In the recent, the aspect of foresight is considered globally important. Specially, it has gained a meaningful position in strategic planning. This study examines the quantitative relationships between strategic foresight, ambidexterity and competitiveness of firms. Based on the literature review, it appears that strategic foresight has positive impact on organisational ambidexterity which in turn contributes to competitive advantage. We have utilised structural equations modeling (SEM) to empirically test the mentioned relationships in Iran's nanotechnology firms. Results show that the degree of strategic foresight has a direct effect on organisational ambidexterity which in turn affects competitive advantage. © 2016 Imperial College Press.
