Three-dimensional isofield micromechanics model for effective electrothermoelastic properties of piezoelectric composites

Abstract

A fully coupled three-dimensional micromechanics model based on the isofield method is developed for the effective electrothermoelastic properties of piezoelectric fiber-reinforced composite (PFRC) materials with poling and an electric field applied normal to the fiber direction. In the isofield method, the strain and electric field components parallel to the plane connecting two phases are assumed to be uniform across both phases, and likewise for the stress and electric displacement components normal to the connecting plane. The model employs the isofield assumptions for two possible connectivities, which are then combined so as to yield transverse isotropy of the effective properties when both constituents are transversely isotropic. The assumption of uniform electric field across two phases made by some existing theories can be achieved as a special case of the present formulation when the dielectric constants of the fiber and matrix phases are equal. The effects of the fiber volume fraction and dielectric ratio on the effective properties are studied for two PFRC systems, PZT-7A/epoxy and PZT-5H/epoxy. The results are compared with those available in the literature based on uniform electric field assumptions. It is found that the dielectric ratio has a very significant effect on the electromechanical and electrothermal coupling constants of PFRCs.