Electromechanical response of piezoelectric composites: Effects of geometric connectivity and grain size

A three-dimensional finite element model has been developed to fully capture the complete electromechanical response of five types of piezoelectric composites (i.e. particulate, short-fiber, long-fiber, laminate and networked composites), the constituent phases of which can, in general, be elastically anisotropic and piezoelectrically active. It is demonstrated that the geometric connectivity of the constituent phases in a composite has a significant influence on the fundamental electromechanical properties and the performance characteristics of a piezoelectric composite. By constructing piezoelectric composite materials design maps, the long-fiber composites (with their highest piezoelectric coupling constants) and interpenetrating networked composites (with their highest piezoelectric charge coefficients) are, respectively, identified as being most suitable for ultrasonic imaging and hydrophone applications. Furthermore, grain size modifications of the constituent phases can significantly enhance the effective piezoelectric properties of a composite such as coupling constants and charge coefficients while maintaining suitable acoustic impedance, especially in the case of the networked composites.