Micromechanical models for the effective time-dependent and nonlinear electromechanical responses of piezoelectric composites

This study introduces micromechanical models for analyzing the overall electromechanical responses of piezoelectric composites comprising polarized piezoelectric ceramics and polymeric constituents. The polarized piezoelectric ceramics can experience nonlinear electromechanical responses due to an application of large electric fields, while the polymer exhibits viscoelastic response. Thus, the piezoelectric composites can experience significant time-dependent and nonlinear electromechanical coupling behaviors. Two micromechanical models are considered: the Mori-Tanaka and unit-cell models. Linearized micromechanical relations are first defined for obtaining the overall responses of the piezoelectric composites followed by iterative schemes in order to correct errors from linearizing the nonlinear responses. Numerical results are presented for two composite systems, that is, piezoelectric unidirectional fiber with circular/square cross section and spherical/cubic particle inhomogeneities embedded in a polymeric matrix. The linear electromechanical responses from the two micromechanical models are compared with the experimental data available in the literature. Parametric studies are performed in order to examine the effect of inhomogeneity geometry and compositions and prescribed boundary conditions on the overall time-dependent and nonlinear electromechanical responses of the composites.