A 3-D Connectivity Model for Effective Piezoelectric Properties of Yarn Composites

Abstract

The purpose of this paper is to develop a 3-D connectivity model that enables better understanding, at the micro-structural level, the effect of fiber orientation, matrix properties, and inter-fiber contact on the effective piezoelectric properties of a composite consisting of a unidirectional piezoceramic fiber yarn in a polymeric matrix. It is assumed in the 3-D connectivity model that the piezoceramic fiber and matrix are connected in parallel in the fiber direction and in series transverse to the fiber direction. The poling direction is at an arbitrary angle from the fiber axis. Using these assumptions and coordinate transformation, the effective piezoelectric properties of yarn composites can be determined. It is concluded that the effective piezoelectric constants are very sensitive to the fiber orientation. There is a significant effect of the dielectric permittivity of the matrix material on the effective piezoelectric constants, and the effective piezoelectric constants obtained from the 3-D connectivity model can change dramatically depending on the non-contact and contact assumptions of the fibers.