Mechanics of Advanced Materials and Structures (15210596)31(12)pp. 2581-2594
In this study, we promote a multi-scale modeling to predict the healing efficiencies (HEs) of incorporated polymers with self-healing microcapsules. The Python scripts were employed to generate three representative volume elements (RVEs) with randomly dispersed 5, 7.5, and 10% volume fraction (VF) of alginate microcapsules. Three VUSDFLD subroutines were codded and supplemented with ABAQUS/Explicit solver to obtain the maximum tensile stresses (Sut) of virgin, damaged, and healed samples followed by calculating HF of self-healing polymers. Based on the simulation results, more incorporation of self-healing microcapsules increased the tensile after impact HF, so that HFs were increased from 46.31% for RVEs containing 5% VF up to 65.41% and 84.84% for 7.5% and 10% VF, respectively. The presence of more self-healing microcapsules could improve the chance of rupturing more filled microcapsules with healing agents after crack propagation due to impact damages in the matrix. Thus, more damaged elements would be healed by spread healing agents. To evaluate the reliability of simulation results, the specimens containing electrosprayed multicore self-healing microcapsules were fabricated, and experimental HFs were calculated. The same trend was obtained for experimental results, as acquired in the simulation of RVEs. The error of healing efficiencies were only 6.82%, 2.81%, and 7.74 for incorporated specimens with 5, 7.5, and 10% VF of electrosprayed multicore microcapsules, respectively, indicating the accuracy of introduced multi-scale finite element modeling. The fabrication defects of experimental specimens can be the reason of simulation errors. © 2023 Taylor & Francis Group, LLC.
Advances in Nano Research (2287237X)16(2)pp. 127-140
Upon direct/indirect exposure to flame or heat, composite structures may burn or thermally buckle. This issue becomes more important in the natural fiber-based composite structures with higher flammability and lower mechanical properties. The main goal of the present study was to obtain an optimal eco-friendly composite system with low flammability and high thermal buckling resistance. The studied composite consisted of polypropylene (PP) and short abaca fiber (AF) with eggshell powder (ESP) and halloysite clay nanotubes (HNTs) additives. An optimal base composite, consisting of 30 wt.% AF and 70 wt.% PP, abbreviated as OAP, was initially introduced based on burning rate (BR) and the Young’s modulus determined by horizontal burning test (HBT) and tensile test, respectively. The effects of adding ESP to the base composite were then investigated with the same experimental tests. The results indicated that though the BR significantly decreased with the increase of ESP content up to 6 wt.%, it had a very destructive influence on the stiffness of the composite. To compensate for the damaging effect of ESP, small amount of HNT was used. The performance of OAP composite with 6 wt.% ESP and 3 wt.% HNT (OAPEH) was explored by conducting HBT, cone calorimeter test (CCT) and tensile test. The experimental results indicated a 9~23 % reduction in almost all flammability parameters such as heat release rate (HRR), total heat released (THR), maximum average rate of heat emission (MARHE), total smoke released (TSR), total smoke production (TSP), and mass loss (ML) during combustion. Furthermore, the combination of 6 wt.% ESP and 3 wt.% HNT reduced the stiffness of OAP to an insignificant amount by maximum 3%. Moreover, the char residue analysis revealed the distinct differences in the formation of char between AF/PP and AF/PP/ESP/HNT composites. Afterward, dilatometry test was carried out to examine the coefficient of thermal expansion (CTE) of OAP and OAPEH samples. The obtained results showed that the CTE of OAPEH composite was about 18% less than that of OAP. Finally, a theoretical model was used based on first-order shear deformation theory (FSDT) to predict the critical bucking temperatures of the OAP and OAPEH composite plates. It was shown that in the absence of mechanical load, the critical buckling temperatures of OAPEH composite plates were higher than those of OAP composites, such that the difference between the buckling temperatures increased with the increase of thickness. On the contrary, the positive effect of CTE reduction on the buckling temperature decreased by raising the axial compressive mechanical load on the composite plates which can be assigned to the reduction of stiffness after the incorporation of ESP. The results of present study generally stated that a suitable combination of AF, PP, ESP, and HNT can result in a relatively optimal and environmentally friendly composite with proper flame and thermal buckling resistance with no significant decline in the stiffness. Copyright © 2023 Techno-Press, Ltd.
This study investigates the effects of incorporating various types of nanoparticles, both singularly and in hybrid form, on the low-velocity impact (LVI) response of glass fiber reinforced polymer (GFRP) composites. GFRP composites were fabricated using the hand lay-up method and different weight percentages (wt. %) of multi-walled carbon nanotubes (MWCNT), clay, TiO2, and CuO nanoparticles were added into the matrix of composites. To test the LVI response, 14 types of specimens were fabricated with single and hybrid nanoparticle loadings, and LVI tests were conducted using 5 and 10-cm span dimensions at two levels of subjected energy. The experimental results reveal that specimens with a single loading of MWCNT or nano-clay have a lower maximum contact force compared to pure specimens with fully rebounding behavior. This indicates that neither 5 nor 10 cm spans result in severe damages during the impact tests. Furthermore, incorporating more MWCNTs results in stiffer behavior and more brittleness. The study also explores the synergetic effect of adding hybrid nanoparticles in the fabricated composites and discusses the calculated results for absorbed energy. Finally, scanning electron microscopy (SEM) images are analyzed to evaluate the enhancement mechanisms resulting from the addition of nanoparticles to GFRP composite specimens. © 2023 The Authors
Materials Today Communications (23524928)36
The aim of this research is to investigate the critical buckling force of a sandwich structure with the addition of nanoparticles to composite faces in an acidic environment. The effect of adding 3 wt% silica and clay nanoparticles in fabrication of composite is compared in mechanical properties and sandwich buckling; And the critical buckling load is obtained by using low order piecewise shear deformation theory (PSDT). In the experimental study, significant degradation is observed after acid immersion, and the addition of 3 wt% nanoclay shows better performance by improving the durability of the structure against changes in the length and mass of the composite specimens. It is shown that the prediction of buckling is a function of mechanical properties, mass absorption, and βacid in acidic immersion, and to determine the buckling response, the mass absorption diagram of the layers, needs to be available. The results imply that the addition of nanoparticles changes the buckling behavior of the sandwich structure, such that the sandwich with silica faces requires more mass absorption than other sandwiches for buckling, however, this composite face have a faster mass absorption rate, which makes their buckling response almost the same as other sandwiches. However the sandwich with the face containing 3 wt% nanoclay still performs better in improving the buckling of the sandwich plate. The findings of the study indicate that immersion in 5% sulfuric acid for 30 days significantly reduced the critical buckling force of composite sandwiches by 63.81–82.25% under simply supported boundary conditions and 29.44–38.97% under clamped boundary conditions. To develop the LOPSDT theory, Ritz method was applied to for clamped sandwich, witch results have been shown very good agreement in validation with the ANSYS solution. © 2023 Elsevier Ltd
The main objective of this study is to investigate the impact of nanoparticles as reinforcement material on the vibrational behavior of sandwich structures in an acidic medium. The glass fiber reinforced polymer (GFRP) faces were fabricated with and without the addition of 3 wt% nanoclay and nanosilica to determine the mechanical behaviors of the GFRP faces in the presence of an acidic medium. The obtained results showed adding 3 wt% of nanoclay caused better durability and less mass variation of composite specimens in sulfuric acid. The “Coefficient of acidic immersion expansion” (βacid) is determined by measuring the length and mass variation of GFRP specimens in the immersion, and applied to low order piecewise shear deformation theory (LOPSDT) for the first time; Also the frequency results of LOPSDT have been shown good agreement in validation with the ANSYS numerical solution. It is shown that acidic environment reduces the frequency of the first mode of sandwich plates with reinforced face by 3 wt% nanosilica, and nanoclay has increased by 6.81 % and 4.66 %, respectively. This study indicates after one month of immersion, the natural frequency of the sandwich with pure, and 3 wt% nanoclay reduces about 1 %, and the natural frequency of the sandwich with the faces reinforced with 3 wt% nanosilica reduces by more than 3 %; Moreover, the frequency of forced vibrations, caused by acidic immersion expansion, was improved significantly by 10.04 % and 6.54 % in the first mode by incorporating 3 wt% of nanoclay, and nanosilica into the faces of the sandwich in one month of immersion compared to the sandwich with pure faces. © 2023 The Authors
Journal of Reinforced Plastics and Composites (07316844)42(3-4)pp. 95-109
The effect of enhancing multicore microcapsules with various nanoparticles on the healing efficiency of microcapsule-based self-healing polymers was investigated in this study. The incorporated polymers with enhanced microcapsules by MWCNT, nanoclay, and nanosilica were fabricated. Three volume fractions (VFs) of microcapsules, including 5, 7.5, and 10% were added to the epoxy matrix. The maximum tensile stresses of the virgin, damaged by controlled low velocity impact test, and healed specimens were obtained to calculate the healing efficiencies of fabricated self-healing polymers. Also, a multi-scale FE modeling was promoted using RVEs generation and ABAQUS-Explicit solver attached with VUSDFLD subroutines to predict the healing efficiencies. The results indicated that by increasing the VF of microcapsules, the healing efficiencies of specimens were increased. Increasing the VF of the microcapsules could increase the probability of hitting induced cracks due to the LVI test with microcapsules. Thus, further spreading of healing agents into the propagated cracks would increase the healing efficiency of specimens containing higher VF of microcapsules. Also, increasing the strength of microcapsules reduced the healing efficiency of specimens. For instance, in the specimens containing 10% VF of enhanced microcapsules with MWCNT, the healing efficiency was 45.90%, while it was 50.41% for enhanced microcapsules with nanosilica. Increasing the mechanical properties of microcapsules could decrease the probability of rupturing damaged microcapsules, which reduced the healing efficiency of these specimens. Finally, the predicted healing efficiency of simulated RVEs had good accuracy, indicating the reliability of introduced multi-scale FEM. © The Author(s) 2022.
Journal of Materials Research and Technology (22387854)24pp. 5042-5058
In this study, the indentation tests are performed with various forces using the Vickers indenter to investigate the mechanical properties, including the elastic modulus, hardness, and the plasticity index of pure, and incorporated glass fiber reinforced polymer (GFRP) composites with nanosilica and nanoclay. To study the effect of adding different nanoparticles on reducing the mechanical properties of immersed specimens in acid for 0, 1 and 3 months, incorporated composite specimens with 3 wt percent (wt. %) of nanoparticles were fabricated using hand lay-up method. Accordingly, the reduction in mechanical properties and increase in plasticity index was attributed to the penetration of acid into composite specimens during the immersion period, which resulted in the failure of matrix and fiber following increased moisture penetration. Adding the nanoparticles especially nanoclay, has alleviated the trend of drop in mechanical properties. In fact, for the incorporated composite specimen with nanoclay, the hardness and elastic modulus of the immersed samples in acid for 0 and 3 months indicated a decrease of 10.55 and 7.88%, respectively on grounds of hydrophobic nature of nanoclay. Conversely, incorporating nanosilica increased the plasticity index leading to higher rate of degradation, which was even more than pure sample, yet the pure sample had the lowest mechanical properties after 3 months of immersion. In addition, Finite element modeling (FEM) and artificial neural network (ANN) were used to respectively predict the indentation behavior of fabricated composite specimens and study the effects of immersion time in an acidic environment. © 2023 The Author(s)
Kamarian, S.,
Khalvandi, A.,
Tran, T.M.N.,
Barbaz isfahani, R.,
Saber-samandari, S.,
Song, J. Advances in Nano Research (2287237X)15(4)pp. 315-328
The main goal of the present study was to assess the effects of eggshell powder (ESP) and halloysite nanotubes (HNTs) on the mechanical properties of abaca fiber (AF)-reinforced natural composites. For this purpose, a limited number of indentation tests were first performed on the AF/polypropylene (PP) composites for different HNT and ESP loadings (0 wt.% ~ 6 wt.%), load amplitudes (150, 200, and 250 N), and two types of indenters (Vickers or conical). The Young’s modulus, hardness and plasticity index of each specimen were calculated using the indentation test results and Oliver-Pharr method. The accuracy of the experimental results was confirmed by comparing the values of the Young’s modulus obtained from the indentation test with the results of the conventional tensile test. Then, a feed-forward shallow artificial neural network (ANN) with high efficiency was trained based on the obtained experimental data. The trained ANN could properly predict the variations of the mentioned mechanical properties of AF/PP composites incorporated with different HNT and ESP loadings. Furthermore, the trained ANN demonstrated that HNTs increase the elastic modulus and hardness of the composite, while the incorporation of ESP reduces these properties. For instance, the Young’s modulus of composites incorporated with 3 wt.% of ESP decreased by 30.7% compared with the pure composite, while increasing the weight fraction of ESP up to 6% decreased the Young’s modulus by 34.8%. Moreover, the trained ANN indicated that HNTs have a more significant effect on reducing the plasticity index than ESP. Copyright © 2023 Techno-Press, Ltd.
Materials Science and Engineering: B (09215107)289
In this study, the synergetic effects of graphene nanosheets (Gr) and copper oxide (CuO) nanoparticles and the hybrid incorporation of both nanoparticles on the mechanical and thermal properties of 8-layer glass/epoxy composites are investigated. Also, the method of hand-lay-up is used and the tensile strength, three-point bending, and low velocity impact tests are performed to study their mechanical properties. Also, the X-ray diffraction (XRD) and Scanning Electron Microscope (SEM) analysis are conducted to study the structure and the morphological behavior of nanoparticles. Finally, the obtained result is that by adding the combination of both nanoparticles to the polymer and fibers, the tensile properties increase about 32 %, its flexural properties increase about 30%. The SEM images show that the less diffuse the copper nanoparticles on the sample surface, the better the activity and dispersion of the graphene nanosheets. The obtained results show that the stress–strain diagram for the sample containing the simultaneous combination of copper and graphene has the lowest stress and yield stress while the pure sample with the highest load tolerance and then the sample contain copper nanoparticles. Also, the interpretation of the obtained results in comparison with the results of other researches shows that the heat transfer behavior is uniformly about 0.1 to 0.3 and the maximum heat transfer rate is 0.38. The results showed that the addition of hybrid CuO and Gr nanoparticles into composite specimens can enhanced both mechanical and thermal properties of fabricated specimens, simultaneously. The equivalent properties of the matrix and graphene nanosheet obtained from the FEM validated by experimental experiments are considered as independent parameters. This equivalent property along with the mechanical properties of the fibers is placed in a quasi-experimental Halpin-Tsai equation to obtain an estimate of the mechanical properties of the whole nanocomposite. © 2022 Elsevier B.V.
Barbaz isfahani, R.,
Khalvandi, A.,
Tran, T.M.N.,
Kamarian, S.,
Saber-samandari, S.,
Song, J. Industrial Crops and Products (09266690)205
The present study investigates the synergistic effects of halloysite clay nanotubes (HNTs) and eggshell powder (ESP) derived from bio-waste on the thermomechanical properties of composites consisting of natural abacá fiber (AF) and polypropylene (PP). First, nine composite sheets of AF/PP incorporating varying loadings of HNTs and ESP (0–6 wt%) were fabricated. The effects of HNTs and ESP on the fracture surfaces of the AF/PP composite using field emission scanning electron microscopy (FESEM) were examined. Subsequently, various experimental tests on the composite samples, including bending tests, differential scanning calorimetry (DSC), and cone calorimeter tests (CCT) were conducted. The results of the bending tests revealed a considerable improvement in the flexural properties of the samples containing HNTs. Specifically, the maximum flexural stress and flexural modulus of the composite containing 6 wt% HNT (H6E0) exhibited approximately 40% and 84% higher values, respectively, compared to the pure AF/PP composite (H0E0). Conversely, the incorporation of ESP had a detrimental effect on the flexural properties of the composites. Additionally, DSC analysis showed an improvement in the thermal behavior of the composite samples upon adding both ESP and HNTs. The results also revealed that while both HNT and ESP had positive effects on the melting temperature (Tm), the impact of ESP was more pronounced. Specifically, the experimental data indicated improvements of 0.9% and 2% in the Tm for the 6 wt% ESP-loaded composite (H0E6) and 6 wt% HNT/6 wt% ESP-loaded composite (H6E6) samples, respectively. Moreover, the CCT results showed that the composite sample containing 3 wt% HNT and 6 wt% ESP exhibited superior flame-retardant performance, indicating significantly improved flammability behavior of the AF/PP composites. © 2023 Elsevier B.V.
Polymer Composites (02728397)43(9)pp. 5929-5945
Microcapsule based glass fiber-reinforced polymer (GFRP) composites have attracted enormous attention due to enhancement of structures' longevity, reducing expenses, and simplicity of fabrication process. In this study, a micromechanical model of a woven E-glass/epoxy composite containing microcapsules was developed based on finite element analysis (FEA). Modified sequential adsorption algorithm was chosen to generate and disperse microcapsules in three types of representative volume elements (RVEs). Also, mechanical properties of microcapsules and composite were assigned based on nanoindentation tests and standard experimental tests, respectively. Eventually, multi-scaling method was implemented to homogenize maximum tensile stress, and subsequent evaluation of tensile after impact (TAI) healing efficiency. Therefore, a healing efficiency of 71% was obtained based on three types of simulations encompassing low-velocity impact (LVI) and quasi-static tensile tests on the RVEs. In order to validate the results; first, an electrospraying set-up was exploited to fabricate multicore microcapsules. The fabricated microcapsules contained mercaptan hardener and epoxy resin as the healing agents, and they were covered by alginate shell. Second, incorporated composite specimens with microcapsules were fabricated via the hand-layup method. The average TAI healing efficiency of 67% was achieved by experimental tests. Furthermore, scanning electron microscope images of the fractured surfaces confirmed rupture of microcapsules in the LVI test. © 2022 Society of Plastics Engineers.
Journal of Composite Materials (00219983)56(18)pp. 2879-2894
In this study, the effect of various microcapsule sizes on the mechanical properties of microcapsule-based polymeric materials was investigated using the finite element method and validated with experimental outcomes. Specimens containing 5wt. % of microcapsules were fabricated to calculate the elastic modulus, and maximum tensile stress, and to validate numerical results. To consider the error, five tests were performed for all samples, and results were reported on average. The average errors between the numerical outcomes and experimental results were 4.74% and 5.35% for maximum tensile stress and elastic modulus, respectively. The coaxial electrospraying method was used for synthesizing microcapsules made of alginate (shell) and epoxy (core). A scanning electron microscope (SEM) was used to calculate the diameter of the capsules. To develop an empirical model for the average microcapsule diameter (AMD) and carry out the optimization process, response surface methodology (RSM) with central composite design was used. Also, analysis of variance was employed to validate the accuracy of the model. The effects of three parameters, including voltage, needle size, and the distance between the tip of the needle to the collector, on average microcapsule diameter, were investigated. The empirical model was validated by a confirmation run, and the determined error (1.93%) between the predicted and experimental results indicates the precision of the model. The numerical study indicated that microcapsule-based self-healing polymers containing smaller microcapsules tolerate higher stresses. However, the effect of the microcapsules’ size on the elastic modulus of a representative volume element was negligible. © The Author(s) 2022.
International Journal of Biological Macromolecules (01418130)200pp. 532-542
A novel method was employed to synthesize microcapsules containing both epoxy and hardener healing agents in a single microcapsule using a two-step electrospraying technique. Moreover, the sodium alginate microcapsule shell was enhanced with three types of nanoparticles, including MWCNT, nanoclay, and nanosilica. The surface morphology of fabricated microcapsules was examined using FESEM and AFM images. The TEM and elemental mapping images illustrated that the added nanoparticles into sodium alginate microcapsule shells were dispersed homogeneously. In addition, the mechanical properties of microcapsule shells were obtained using nanoindentation tests. Based on this research, the addition of nanoparticles increased the size and the roughness of microcapsules and improved the elastic modulus and the hardness of microcapsule's outer shells, significantly. For instance, the elastic modulus and the hardness of incorporated microcapsule shells with MWCNT increased by 85.5% and 91.3%, respectively, compared to neat sodium alginate multicore microcapsules, due to intrinsic high strength and high aspect ratio of MWCNT. © 2022
Barbaz isfahani, R.,
Dadras, H.,
Taherzadeh-fard, A.,
Zarezadeh-mehrizi, M.A.,
Saber-samandari, S.,
Salehi, M.,
Liaghat, G. Fibers and Polymers (12299197)23(7)pp. 2003-2016
Different loadings of single and hybrid MWCNT, CuO, TiO2, and clay nanoparticles were incorporated into glass fiber reinforced polymer (GFRP) composites to investigate the synergetic effects of nanoparticles addition on tensile, flexural, and quasi-static behaviors. Fourteen types of incorporated GFRP composites were fabricated using hand layup method. The results showed that the addition of single loading of MWCNT can improve mechanical properties of GFRPs, significantly. For instance, incorporation of 0.3 wt. % MWCNT led to 40 % enhancement of elastic modulus and 66 % increasing of maximum tensile stress, compared to neat GFRP composites. Moreover, the hybrid addition of MWCNTs and CuO nanoparticle could increase tensile properties of incorporated GFRP composites, significantly; due to synergetic effect of hybrid addition of nanoparticles. Based on flexural tests, specimen containing 0.3 wt. % MWCN+1 wt. % TiO2+0.5 wt. % CuO and specimen containing 0.3 wt. % MWCNT+0.5 wt. % CuO have shown the highest elevation of bending properties among hybrid composites. Quasi-static test results illustrated that incorporated GFRP composites with 0.5 wt. % of MWCNT with the span length of 7×7 mm2 resulted in significantly higher peak load. Finally, FESEM and elemental mapping images were examined to study the enhancement mechanisms and the state of nanoparticles’ dispersion into the fabricated GFRP specimens. © 2022, The Korean Fiber Society.
Mechanics Based Design of Structures and Machines (15397742)49(2)pp. 217-232
The first aim of this article is to experimentally explore the effect of multi-walled carbon nanotubes (MWCNTs) on the coefficient of thermal expansion (CTE) of epoxy-based composites. Focusing on the obtained experimental data, two important conclusions can be drawn. (1) Though the CTE of carbon nanotubes (CNTs) is lower than that of neat epoxy, using more CNT does not necessarily decrease the CTE of epoxy polymer. (2) The optimum weight percentage of CNT is 0.3 which can reduce the CTE of epoxy up to 33%. As the second goal of the present research work, thermal buckling analysis of rectangular carbon-fiber-reinforced CNT/epoxy polymer (CFRCNTEP)-laminated composite plates is performed numerically. To this purpose, first, using the obtained experimental data and micro-mechanical models, the thermo-elastic properties of structure are calculated. Then, based on the first-order shear deformation theory (FSDT) and by means of generalized differential quadrature (GDQ) method, the influence of CNTs on the critical buckling temperature of CFRCNTEP composite plates is investigated. The numerical results reveal that MWCNTs can strongly affect thermal buckling behavior of composite plates. It is observed that by adding 0.3 wt. % CNTs into the matrix phase, the critical buckling temperature increases between 35 and 42%. © 2019 Taylor & Francis Group, LLC.
Qian, W.,
Vahid, M.H.,
Sun, Y.,
Heidari, A.,
Barbaz isfahani, R.,
Saber-samandari, S.,
Khandan, A.,
Toghraie, D. Journal of Materials Research and Technology (22387854)12pp. 1931-1945
In recent decades, polymer composites are widely used in industry due to their good mechanical properties and their low specific weight. Also, the use of glass fibers and carbon nanotubes can strengthen and improve the mechanical performance of the polymer due to their good mechanical properties. In this study, incorporated glass/epoxy nanocomposite with carbon nanotubes (CNT) samples were fabricated using a hand lay-up process, and the effect of addition functionalized Single-Walled Carbon Nanotubes (F-SWCNT) with COOH and non-functionalized SWCNT was investigated. The tensile strength, elastic modulus, bending strength was obtained experimentally using SANTAM-STM50. X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM) were used to investigate the phase and morphology of the fibers. The mechanical properties results showed that the highest elastic modulus and tensile strength are obtained for the sample reinforced with F-SWCNT which increased by 32% and 10%, respectively in comparison with pure epoxy. Also, the obtained results of the bending test indicate that the highest flexural modulus and the highest flexural strength are related to the sample reinforced with functionalized carbon nanotubes which are 16.9 GPa and 381.39 MPa, respectively. Then, the mechanical performance of the reinforcement in the epoxy matrix and the failure mechanism was monitored using SEM images. Finally, reinforced epoxy nanocomposites with functionalized and non-functionalized SWCNT were simulated using Molecular Dynamics (MD) simulation to examine the agreement with the trends of experimental results. The MD obtained results showed that the most appropriate mode of dispersion occurs when functionalized carbon nanotubes are used. Also, it was observed that the elastic modulus of incorporated nanocomposites with F-SWCNT increased by 17% compared to non-functionalized SWCNT which shows the agreement with the trends of experimental results. © 2021 The Author(s).
Journal of Composite Materials (00219983)55(27)pp. 3989-4010
Investigation and analysis of the dynamic behavior of composite materials and their failure resistance are essential. The main aim of this study is to investigate the improvement of impact properties of incorporated glass fiber reinforced polymer (GFRP) composite specimens with various loading of nanoclay and nanosilica in a corrosive environment. After fabrication of samples by hand layup method, all of them were immersed in 5 wt. % of sulfuric acid solution for 0, 1 and 3 months. As the immersion time increased, the specimens containing nanosilica absorbed more water than the other samples. The force-displacement, force-time and energy-time diagrams showed the superiority of filled composites with nanoparticles over the pure sample in all immersion periods. Low-velocity impact (LVI) test results of specimens containing nanoclay showed a better behavior and with the addition of 5 wt. % of nanoclay, the impact force increased by 15.72% and the displacement decreased by 5.26%. Also, in these samples, the energy absorption rate decreased by 17.15%, which was associated with a reduction in the damage rate. After immersion of specimens in different times, specimens containing 5 wt. % of nanoclay had better strength than other samples and maintained their superior properties. The obtained results illustrated that the addition of 1 and 3 wt. % of nanosilica had no specific effect on the improvement of impact properties. Finally, incorporated GPRP composites with 3 wt. % of nanoparticles were simulated using LS-DYNA software and the experimental and numerical results were compared to investigate their accordance. © The Author(s) 2021.
Sun, C.,
Yarmohammadi, A.,
Barbaz isfahani, R.,
Ghadiri nejad m., M.G.,
Toghraie, D.,
Fard, E.K.,
Saber-samandari, S.,
Khandan, A. Journal of Molecular Liquids (18733166)325
In the present study, a group of microcapsule-based smart coatings has been investigated to decrease the corrosion rate in oil and gas transmission lines. The microcapsules are made of epoxy resin and self-healing materials such as oil, which acts as a repairing agent. In this study, the parameters affecting the coating performance such as agitation rate in the micro capsulation process, microcapsule size, and percentage of microcapsule used in the coating structure have been investigated and optimized. Also, other properties of the smart coating, such as the ability to protect against corrosion and adhesion of the coating to the substrate, are examined by Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD) analysis, and pull-off test. The use of microcapsules indicates that as the microcapsules become smaller, the corrosion resistance, as well as the adhesion of the coating to the substrate, is improved. Also, the use of microcapsules in the structure improves the protective capability significantly. The best percentage of microcapsules is the sample with 40 wt%, which increases the corrosion resistance of the coating, although the polymers increase the results of electrochemical and water absorption tests. The formation of microcracks is a serious problem in the use of polymers composites. The creation and spread of these microcracks cause the destruction of these materials and reduces the lifetime of the polymeric material. Above for the synthesis of microcapsules, the method of preparing self-healing polymers and adding them to the containing 40% of microcapsules may provide a suitable coating for carbon steels of oil and gas industries along with a suitable model of its molecular dynamics simulation (MDs). © 2020 Elsevier B.V.
Iranian Journal Of Materials Science And Engineering (17350808)18(2)pp. 1-12
The low velocity impact (LVI) response of a pure and glass fiber reinforced polymer composites (GFRP) with 0.1, 0.3 and 0.5 wt.% of functionalized single-walled carbon nanotubes (SWCNTs) was experimentally investigated. LS-DYNA simulation was used to model the impact test of pure and incorporated GFRP with 0.3 wt. % of SWCNT in order to compare experimental and numerical results of LVI tests. All tests were performed at two different levels of energy. At 30J energy, the specimen containing 0.5 wt. % SWCNT was completely destructed. The results showed that the incorporated GFRP with 0.3 wt. % SWCNT had the highest energy absorption and the back-face damage area of this sample was smaller than other specimens. TEM images from specimens were also analyzed and showed the incorporation of well-dispersed 0.1 and 0.3 wt. % of SWCNT, while in specimens containing 0.5 wt.% of CNT, tubes tended to be agglomerated causing a drop in the LVI response of the specimen. The contact time of the impactor in numerical and experimental results was approximately equal. However, as the conditions in numerical modeling are considered ideal, the maximum contact forces in LS DYNA simulation results were higher than the experimental results. © 2021, Iran University of Science and Technology. All rights reserved.
Journal of Sandwich Structures and Materials (15307972)23(8)pp. 3606-3644
Previous studies on the thermal buckling of sandwich plates with composite face sheets indicate that only thin skins with high stiffness and low coefficients of thermal expansion (CTE) can lead to the desired buckling temperatures. Thus, carbon nanotubes (CNTs) that can significantly enhance thermo-mechanical properties of fibre-reinforced polymer composites are used in the present study to increase the critical buckling temperature of sandwich plates with soft core and laminated composite face sheets. First, a comprehensive series of experimental tests are conducted to evaluate the effects of nanotubes on thermo-mechanical properties of the face sheets. The experimental results indicate that using only 0.3% CNTs considerably increases the longitudinal and transverse Young’s modulus and shear modulus of the carbon fibre/epoxy composite face sheets. The obtained data also show that CNTs significantly decrease the CTE of composite skins. Subsequently, thermal buckling equations of sandwich plates with CNT-reinforced composite face sheets are derived based on piecewise low-order shear deformation theory (PLSDT). Three analytical, semi analytical, and numerical methods are used to investigate thermal buckling behaviour of the sandwich plates with various boundary conditions. To verify the results, several comparisons are performed, which show that the implemented methods can predict the buckling temperatures of sandwich plates with high accuracy. Finally, a parametric study is conducted to examine the effects of CNTs on the thermal buckling of sandwich plates for different length to thickness ratios, thicknesses of face sheets, stacking sequences of layers, and various types of boundary conditions. The results indicate that CNTs can increase the critical buckling temperature of sandwich plates by 22%–36%, based on the layup, geometrical parameters, and boundary conditions. © The Author(s) 2020.
Mechanics Based Design of Structures and Machines (15397742)pp. 1-24
One of the essentials for designing composite structures exposed to heat is the correct choice of reinforcing materials. In the present research work, a comparison is made between the performances of two well-known advanced materials, Shape Memory Alloys (SMAs) and Carbon Nanotubes (CNTs), in thermal bucking behavior of thin composite beams with simply supported boundary conditions. First, the effect of embedding SMA wires on the thermal buckling of laminated composite beams are examined. The stability equations are derived based on Timoshenko Beam Theory (TBT), and the critical buckling temperatures are obtained analytically. The advantages and disadvantages of using SMA wires as well as their proper functional range are studied. Then, in the next step, the influence of CNTs on the thermal buckling response of composite beams is presented. To this end, the results of some experiments such as Dynamic Mechanical Thermal Analysis (DMTA) and Thermo-Mechanical Analysis (TMA) tests are used to obtain thermal properties of CNT-reinforced composite materials. The performance of CNTs is also evaluated in comparison with SMA wires. It is found from the analysis that, depending on the structural conditions, one reinforcing material can outperform the other. Finally, the idea of simultaneous use of both reinforcing materials comes up. The results show that, in some circumstances, the use of only one of the SMAs or CNTs does not have significant effect on the thermal buckling of composite beams, but applying both of these advanced reinforcing materials in the composite medium can extraordinarily enhance the critical buckling temperatures. © 2020, © 2020 Taylor & Francis Group, LLC.
Molecular Simulation (08927022)46(6)pp. 476-486
In this study, the mechanical properties of graphene–epoxy nanocomposites were investigated using experimental tests, molecular dynamics (MD) simulation and Halpin_Tsai semi-empirical micromechanical model. To fabricate graphene/epoxy nanocomposite, specimens containing 0, 0.3, 0.5 and 0.7 weight percent (wt.%) of graphene nanoparticle (GNP), high power dispersion sonicating method and high-speed shearing were employed. Then, tensile and flexural modulus of manufactured nanocomposites were obtained, and the results illustrated that the elastic and flexural modulus of GNP/epoxy nanocomposites increased significantly until GNP was added up to 0.5 wt.% and after that, the trend of increasing elastic modulus declined which could be due to local GNP agglomerations within the nanocomposites with higher contents of filler. Furthermore, graphene, epoxy and graphene–epoxy nanocomposites were simulated by MD, and the mechanical properties of simulated graphene–epoxy nanocomposites were calculated. However, the effect of temperature and strain rate on tensile properties of graphene–epoxy nanocomposites was studied, which showed that increasing temperature decreased the strength of graphene–epoxy nanocomposites, and also increasing the strain rates led to an increase in the elastic modulus. Finally, experimental results and the Halpin_Tsai model were compared in which a good agreement between experimental and analytical results was observed. © 2020, © 2020 Informa UK Limited, trading as Taylor & Francis Group.
Composites Part B: Engineering (13598368)175
In this study, the elastic modulus of single-walled carbon nanotubes (SWCNTs)/epoxy nanocomposite was studied using the 3D finite element method and compared with experimental results to investigate the effect of SWCNTs interphase, curvature, and agglomeration on the prediction of the elastic modulus. Nanocomposite specimens containing 0.1, 0.3, and 0.5 wt% SWCNTs were fabricated to obtain SWCNTs/epoxy elastic modulus. The elastic modulus increased until SWCNTs was incorporated up to 0.3 wt% and after that, the trend of increasing elastic modulus declined. TEM images showed that in higher contents of filler, there were some local SWCNTs agglomerations within the composites which caused a dropped in elastic modulus of specimens containing 0.5 wt% SWCNTs. Also, six different 3D representative volume element (RVE) of SWCNTs/epoxy including incorporated cylindrical, cylindrical with agglomeration, curved-cylindrical, cylindrical with interphase, cylindrical with interphase and agglomeration and curved-cylindrical with agglomeration SWCNTs in the epoxy matrix have been generated using Digimat-FE and their elastic modulus evaluated by Digimat-FE solver. The numerical results cleared that the simplest cylindrical RVE has the greatest discrepancy with experimental results which showed the necessity of consideration of three important parameters including SWCNTs interphase, curvature, and agglomerations. By considering SWCNTs interphase and agglomeration the difference of numerical and experimental results decreased so that in specimens containing 0.1 wt% SWCNTs the error was only 6.8%. Also, the best results obtained from RVE of curved-cylindrical with agglomeration in specimen containing 0.1 wt% SWCNTs with only 4.1% error which showed the importance of considering SWCNTs agglomeration and curvature for modeling of nanocomposites. © 2019 Elsevier Ltd
Proceedings of the Institution of Mechanical Engineers, Part L: Journal of Materials: Design and Applications (20413076)233(5)pp. 874-884
In this study, the effects of nano- (Formula presented.) and carbon nanotubes on the friction and wear properties of carbon-epoxy woven composites have been explored. The unfilled carbon fabric composites and carbon fabric composites filled with carbon nanotubes and nano- (Formula presented.) were fabricated by vacuum infusion process. The worn surfaces were examined and possible wear mechanisms of unfilled and filled carbon fabric composites were discussed. In addition, the friction coefficient curves of unfilled and filled carbon fabric composites were analyzed and compared. The experimental results showed that either of the two nano-particles improved the friction coefficient and wear rate of carbon fabric composites; however, better improvement was observed for nano-SiO 2 . By adding these nano-particles to unfilled carbon fabric composites, a primary steady-state period with a low friction coefficient appeared in the friction coefficient curve of the composites, which indicates enhancement in bonding strength between carbon fiber and epoxy matrix due to the interfacial reinforcing action of the nano-particles. © IMechE 2017.
Theoretical and Applied Fracture Mechanics (01678442)96pp. 272-284
An epoxy matrix incorporated with hybrid multi-walled carbon nanotube (MWCNT) and nanosilica was used to fabricate woven carbon fabric epoxy composites using vacuum-assisted resin infusion molding (VARIM). Three types of multi-scale hybrid composites containing 0.2 wt.% MWCNT + 0.7 wt.% nanosilica, 0.7 wt.% MWCNT + 0.2 wt.% nanosilica, and 0.45 wt.% MWCNT + 0.45 wt.% nanosilica were prepared to investigate both tensile and tribological properties, simultaneously. The results of tensile and tribological experiments showed that specimens containing 0.45 wt.% MWCNT + 0.45 wt.% nanosilica were better than the corresponding single-type nanoparticles with the same total weight percentages. Especially, the tensile strength and tensile modulus of composite specimens containing 0.45 wt.% MWCNT + 0.45 wt.% nanosilica increased by 25.2% and 31% in comparison with the neat composites, while their friction coefficient and wear rate decreased by 88% and 98% in comparison with the neat composites, respectively. The SEM images of fracture surfaces showed that the incorporation of nanoparticles enhanced the fiber–matrix interfacial strength, toughened the surrounding matrix, and improved resin adhesion to the fiber, which increased tensile properties of incorporated composites with hybrid nano-fillers. Moreover, by adding the hybrid nanoparticles to the unfilled carbon fabric composites, the friction coefficient variation of these specimens totally changed, which led to an improvement in the friction-reducing ability and wear rate resistance. In conclusion, a method is suggested in this paper to incorporate hybrid nanoparticles for benefitting from the properties of both nanoparticles at higher weight percentages. © 2018 Elsevier Ltd
Journal of Composite Materials (00219983)51(30)pp. 4177-4188
The effects of multi-walled carbon nanotubes (MWCNTs) and nanosilica on tensile behavior of woven carbon fabric-reinforced epoxy composites have been studied. Multi-scale composites with epoxy matrices modified with different MWCNT and nanosilica contents (0.1, 0.5 and 0.9 wt.%) have been fabricated by vacuum-assisted resin infusion molding (VARIM). The dispersion of the nanoparticles in the epoxy resin has been made using an ultrasound and high-speed shearing method. Incorporation of nanoparticles improved tensile behavior and this effect was more evident in the case of composites reinforced with 0.5 wt.% of MWNCT and nanosilica. Incorporating either of the tow nanoparticles at 0.9 wt.% leads to a decrease in the trend of tensile properties. Examination of fracture surfaces using scanning electron microscopy (SEM) showed that by incorporating 0.9 wt.% of each nanoparticle, there are local MWCNT and nanosilica agglomerations within the composites. These nanoparticle-agglomerates reduced their potential strengthening effect in multi-scale composites containing 0.9 wt.% of nanoparticles. Also, SEM images showed that the MWCNTs and nanosilica enhanced the fiber–matrix interfacial strength and then by toughening the surrounding matrix, improved the strength and stiffness of multi-scale composites. © 2017, © The Author(s) 2017.
