Failure and volume fraction dependent mechanical properties of composite sensors and actuators

Composite actuators and sensors manufactured by combining a ferroelectric ceramic such as lead zirconate titanate and a passive phase such as a polymer are used in a variety of applications including SONAR, vibration damping, change of structural shape (morphing), and structural health monitoring. The composite route provides specific advantages, including tailored piezoelectric response, high strain, a degree of flexibility, and increased damage tolerance compared with conventional dense monolithic ceramic materials. For piezoelectric fibre composites, where fine-scale brittle ceramic fibres of 40-800 mu m diameter are introduced into a ductile polymer matrix, the composite strength and failure mechanism ultimately depend on the mechanical properties of each phase and their volume fraction. This article examines the mechanical properties of piezoelectric fibres and the matrix phase and discusses the possible influence of fibre volume fraction on mechanical properties and failure mechanism of the composite. The data are of particular use in determining the failure stress, failure strain, and failure mechanism of composite actuators and sensors subjected to high levels of stress, for example, in applications where such devices are embedded into host structures.