Influence of geometry and material properties on the optimum performance of the C-shape piezo-composite actuator

Abstract

In recent years, due to rapid advances in technology there has been an increasingly high demand for large displacement and large force, precise positioning, fast response, low power consuming miniature piezoelectric actuators.

In certain smart structure applications, the use of curved piezoelectric actuators is necessary. The present work extends the earlier investigations on the C- shape actuator by providing a detailed investigation on the influence of geometric and material properties of the individual layers of the C-shape piezocomposite for its optimal performance as an actuator.

Analytical models have. been used to optimize the geometry of the actuator. Experimental and finite element analyses (using general purpose finite element software i.e. CoventerWare and MSC. Marc) have been used for validation.

The present work has established that, by maintaining the thickness of the substrate and piezoceramic layers constant; changing the external radius, for example increasing it, the stiffness of the structure decreases and thus yielding large displacement This has a negative effect on the force produced by the actuator.

With fixed thickness of the substrate and varying the thickness of the piezoceramic (for fixed external radius) the result is as follows: Increasing the thickness of the piezoceramic layer has the effect of decreasing the displacement while the force increases.

With fixed PZT thickness as well as the external radius, varying the substrate thickness has the following effect: As the thickness of the substrate increases the displacement increases reaching a maximum. Subsequent increase in the thickness of the substrate the displacement is reduced. The force continues increasing at least for the ratios up to 1.0, further increase of the substrate, subsequent decrease of force is also noted. In addition to changing the thickness of the substrate, the choice of different material for the substrate has the following effect: For substrate/PZT ratios of up to 0.6. an actuator with substrate material having higher elastic modulus will produce larger displacement while for ratios beyond this ratio the situation is reversed. The causes for this kind of behaviour have been addressed.

In all cases both force and displacement are found to be directly proportional to applied voltage.