The effect of polymer on piezoelectirc fiber composites actuators

Piezoelectric fiber composites is one of the new type piezoelectric devices for actuators, since it has obvious anisotropy as well as high toughness that couldn´t be gotten from normal piezoceramics. Piezoelectric fiber composites is denominated by piezoelectric fiber, polymer and interdigitated electrode layer. Through design processes, better mechanical and electrical characteristics than piezoceramic materials can be obtained. Its theory model is not founded completely yet because of the complexity of this device. So a series of piezoelectric unit´s equations about longitudinal length extension vibration mode are established. According to the dynamic FEM (finite element method) equations for piezoelectric actuators, which were established by means of Lagrange function and Hamilton principle, some finite models are established. Then, the effect of polymer´s material characteristics on performance of actuators is studied. The results show that piezoelectric fiber composites has orthotropic properties. And the strain of piezoelectric fiber composites can be improved markedly by employing polymer with larger permittivity, Poisson ratio or smaller elastic modulus. At the same time the stress of actuators is studied. In addition, the effect of polymer´s thickness and material constants around electrodes are studied. Several rules summed. At last, the maximum strain (170 mu ) is got from the numeric model of optimized samples, which is very large considering composites.