RESIDUAL STIFFNESS AND ACTUATION PROPERTIES OF PIEZOELECTRIC COMPOSITES - THEORY AND EXPERIMENT

This work attempts to characterize and model the effective stiffness a nd actuation properties of active composite materials under high uniax ial tensile loads. The motivations for this undertaking are to obtain effective material properties as damage accumulates in the active elem ent and to identify the mechanisms affecting stiffness and actuation t o improve the material. A unified model with predictive capability for overall laminate effective material properties was developed. Key mod el assumptions include a constant linear elastic fiber recovery length and a Weibull form for fiber strength. A one dimensional shear lag mo del was employed to characterize the load transfer between the composi te's layers. In order to validate this model several experiments were conducted on interdigitated electrode piezoelectric fiber composites e mbedded in E-glass laminae. Actuation data were obtained by performing active tests: specimens were subjected to increasing tensile loads an d measurements of actuation under load were taken at selected strain l evels. Stiffness data was collected during actuation tests. Very good correlation was demonstrated in most cases between predicted behavior and experimental results.