Finite element modeling of temporal evolution of the quasi-piezoelectric d33 coefficient of cellular piezoelectret Polypropylene film

Voided charged polymer film, also called cellular piezoelectret, shows quasi-piezoelectric response macroscopically. The piezoelectric d33 coefficient can be as large as that of Lead Zirconate Titanate ceramics. Because of the inherent viscosity of polymer, the piezoelectric d33 coefficient of cellular piezoelectret is time-dependent. In this article, the effective piezoelectric d33 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 d33 coefficient is obtained in terms of the converse piezoelectric effect. Qualitative analysis of temporal evolution of the effective piezoelectric d33 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 d33 coefficients of cellular piezoelectret Polypropylene film published in literature.