Predicting the deformation characteristics of rectangular unsymmetrically laminated piezoelectric materials

Abstract

A theory is presented which can be used to explain the room-temperature shape, specifically the curvature of the out-of-plane deflections, of the laminated piezoceramic material known as THUNDER. Because of its unsymmetric laminated construction, THUNDER exhibits unusual deformation characteristics as it cools from its elevated cure temperature to room temperature. The theory, which was originally used by the first author for the study of unsymmetrically laminated fiber-reinforced composite materials, predicts the cooled shape can be spherical, or one of two near-cylindrical shapes. Which shape actually occurs depends on the geometry of the laminate. When the laminate assumes one of the two near-cylindrical shapes, it can be changed to the other near-cylindrical shape by a simple snap-through action. Thus, stability is an issue and is examined. The theory is extended to explain the deformation response of THUNDER to an electrical field applied to produce dilatational strains in the piezoceramic. In general, the applied field changes the curvatures of the laminate in linear proportion to the field strength and the laminate remains basically the same shape. However, it is shown that under certain conditions the applied field has the potential for changing the laminate from one near-cylindrical shape to the other.