DYNAMIC-RESPONSE OF INITIALLY LOADED PIEZOELECTRIC PLATES COMPOSED OFSHORT FIBERS

The vibration behavior of piezoelectric plates under initial electrome chanical loads is examined. A unified mi cromechanics approach is adop ted for determining the effective electroelastic properties of composi te composed of short fibers. The fibers are treated as spheroidal incl usions. Both the matrix and inclusions are assumed to be linearly piez oelastic and transversely isotropic. The electroelastic Eshelby tensor s for ellipsoidal inclusions have been obtained and also evaluated num erically for finite fiber aspect ratios. Utilizing these tensors and a pplying the Mori-Tanaka mean field theory to account for the interacti on between inclusions and matrix, the effective electroelastic propert ies of the composites are obtained. These properties are then used to evaluate the vibration behavior of the plates subjected to preexisting electromechanical lends. The Trefftz equations and the variational pr inciple are used to account for initial stresses. Numerical examples a re given for the BaTiO3/PZT-5H and carbon/PZT-5H composites. The effec ts of piezoelastic coupling on the elastic moduli and fundamental freq uency have been assessed. It is found that piezoelastic coupling provi des a stiffening effect on the material, thus increasing the fundament al frequency of the plate. The influence of piezoelastic coupling is m ore pronounced when shorter fibers are used. The coupling effects vani sh when the material becomes monolithic. Similar to applied mechanical loads, initial electric fields also affect the dynamic response of th e plate, and plate buckling can occur when the applied initial electro mechanical loads reach critical values.