Connectivity and shape effects on the effective properties of piezoelectric–polymeric composites

This paper reports the influence of connectivity and shape of constituent phases on the effective electroelastic coefficients of a diphasic composite, either piezoelectric fibers in a polymer matrix (PZT–polymer) or the reverse (polymer–PZT). Four basic connectivity orders 3-0, 3-1, 3-2 and 3-3 are considered, in which the matrix phase is self-connected in all three directions and the fiber phase is self-connected in zero, one, two and three directions, respectively. The four fiber shapes considered are circular cylinder, elliptical cylinder, touching circular cylinders and triangular prism. The calculations are carried out using finite element modeling of eight unit cells. A detailed study shows that (1) connectivity can drastically alter the effective properties by as much as an order-of-magnitude at the same fiber volume fraction, (2) the fiber shape has significantly less influence on the coefficients compared to connectivity or fiber volume fraction, (3) connectivity orders exert different impacts on the various effective coefficients, and (4) connectivity and fiber volume fraction effects are comparable in PZT–polymer but the latter effect is stronger in polymer–PZT.