Effect of mechanical load on resultant composite piezomodules

Abstract

A mathematical model has been developed and, on its basis, analytical solutions have been found for the resulting "reduced" electroelastic characteristics, in particular, for deformation (shear) piezomodules and dielectric permeabilities of a transversal-isotropic piezoelectric material (composite), taking into account corrections due to the presence of mechanical axial stresses and electrodeformational reorientation of the axis of symmetry of the material properties under the action of an electric field. In the initial configuration, axial tensile and/or compressive stresses do not result in shear strains of the material, the shifts are initiated by the application of an electric field and are "amplified" by axial stresses of the initial configuration. The effect of increasing the resulting values of deformation piezomodules of the material from the action of axial stresses was revealed. The values of the applied axial stresses do not exceed the values of the loss of stability of the material (elements of the structure and, in general, the composite), which causes the preservation of the effect of increasing piezomodules also under the action of an alternating electric field. The results of numerical modeling are obtained for the transversal-isotropic polymer composite "silicone/PZT-4" with unidirectional piezoelectric fibers with a circular cross section as a partial (limit) case of the structure with oriented ellipsoidal inclusions using the known "generalized singular approximation" based on the method of Green functions of statistical mechanics of composites for calculating tensors of effective properties composite in the current configuration. Deformation anisotropy corrections are calculated through the current coordinates of the guide vector for the symmetry axis of the properties - the orientation direction of the fibers of the composite. It has been found that the most significant effect of increasing shear piezomodules is manifested for a unidirectional fibrous composite with a low-modulus polymer matrix "silicone/PZT-4" at small values of the volume fraction of rigid piezoelectric fibers from the action of compressive longitudinal axial stress.