Analysis of Coiled Piezoelectric Structures

Abstract

This study is concerned with piezoelectric bimorph structures of novel shape. A bimorph is a thin strip with two layers of actuating material that enable the strip to bend and to extend independently of the applied loads under electrical control; the associated generalised Hooke’s law is derived by simple means. This approach complements the analysis of, first, a straight helix and, second, a coiled-coil, which have been recently proposed as actuators of relatively large displacements. Two specific quantities are obtained in closed form as measures of overall performance for each actuator; the freely actuated displacement and the load required to restore this displacement to zero. It is shown that a coiled-coil greatly magnifies small actuation strains at the expense of a low load-carrying capacity.