Improved modeling of 0:3 composite materials

Composite materials comprising a packing of hard, dense materials embedded in a soft, light polymer matrix are frequently encountered in ultrasonic transducer design. An important class of material is the 0:3 piezoelectric composite comprising piezoelectric ceramic particles dispersed in a polymer matrix. In this case, as well as desiring an estimate of the elastic properties, predictions of electrical conductivity and dielectric permittivity are also valuable. A brief review of some important composite models is followed by the development of a new expression for predicting the conductivity of composite materials. This model takes account of particle volume fraction, packing pressure, number of contacts per particle and constituent particle material properties. Some limited experimental verification is presented. In the process of developing the expression, key factors important to successful composite design become evident.