Finite element modeling of temporal evolution of the quasi-piezoelectric d ₃₃ coefficient of cellular piezoelectret Polypropylene film

Voided charged polymer film, also called cellular piezoelectret, shows quasi-piezoelectric response macroscopically. The piezoelectric d ₃₃ coefficient can be as large as that of Lead Zirconate Titanate ceramics. Because of the inherent viscosity of polymer, the piezoelectric d ₃₃ coefficient of cellular piezoelectret is time-dependent. In this article, the effective piezoelectric d ₃₃ coefficient of cellular piezoelectret is simulated by means of the finite element method. The cellular piezoelectret film is regarded as the periodic composite material, where the closed flat voids are scattered periodically. The hollow oblate tetrakaidecahedron is used to model the void in a representative volume element. The polymer is taken to be isotropic and viscoelastic. The electrostatic field and the deformation are numerically solved. The piezoelectric d ₃₃ coefficient is obtained in terms of the converse piezoelectric effect. Qualitative analysis of temporal evolution of the effective piezoelectric d ₃₃ coefficient is presented with respect to various parameters, including the microstructural void parameters, charge density as well as the viscoelastic parameters. Finally, this finite element model is used to simulate the experimental results of the effective piezoelectric d ₃₃ coefficients of cellular piezoelectret Polypropylene film published in literature.