Finite Element Modelling of 3-3 Piezocomposites

Efforts to improve the properties and reliability of piezoelectric materials have often concentrated on processing dense ceramic material by techniques such as fine particle size powder production, grain size control, hot pressing, hot isostatic pressing and controlled atmosphere sintering [1–3]. However, it has been shown that lowering the density and introducing significant amounts of open porosity into a piezoelectric material can lead to large improvements in its performance for specific applications, such as low-frequency hydrophones [4–8]. Due to the microstructural connectivity, these open porosity structures are termed 3-3 piezoelectric composites or piezocomposites. In this convention the first digit refers to the connectivity of the active piezoelectric phase while the second digit refers to the inactive phase, which is air or a flexible polymer [9]. The interest in piezocomposite materials is due to a demand for low frequency hydrophone/actuator devices for use in underwater acoustic systems typical of those encountered in Navy sonar array applications and also in civilian applications such as oil reservoir monitoring, seismic monitoring, bio-acoustic research and general oceanographic applications [10]. Parameters to consider for hydrophone applications are sensitivity, impedance, depth capability, frequency range and cost.