Modeling of poling behavior of ferroelectric 3-3 composites

Piezoelectric 3-3 composites are often prepared from unpoled PZT ceramics and polymer matrices. During the poling process the PZT cannot deform freely due to the clamping by the surrounding polymer, which after poling results in the occurrence of residual mechanical stress in the composite. Based on the multi-linear constitutive model of ferroelectric and ferroelastic piezoceramics, a nonlinear finite element analysis was performed within the representative volume element to model the poling behavior of this kind of composites, in which appropriate periodic boundary conditions were prescribed for the displacements and the electric field of the composites. Considering the fact from experimental data that changes of the remanent strain induced by the switching process are volume preserving, we introduced different criteria in evaluating the maximum and minimum values of the ferroelastic strain Sf. A numerical simulation was then conducted to investigate the effects of different poling voltages and volume fractions of the PZT ceramic on the distribution of residual mechanical stress in the PZT of composites. The results show that if Vf < 18% a portion of the compressive mechanical stress in the poling direction on the PZT ceramic may cause a mechanical depolarization of the PZT ceramic.