Energy Harvesting Performance of off-Axis PZT-7A Fiber-Reinforced PVDF Piezoelectric Composite Structures — A Computational Micromechanics-Based Study

Abstract

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.