Processing of piezoelectric fiber/polymer composites with 3-3 connectivity

The processing-property relationship of dielectric and piezoelectric properties of 3-3 fabric composites was studied. Fine PZT green fibers were woven into plane fabric, cut in 3 x 3 cm(2) pieces, and stacked 8 plies high. The stacks were heat-treated with and without applied pressure and then embedded in soft and hard polymers. Increasing the applied pressure increased the density and electromechanical properties of composites due to the improvement of the ply-to-ply sintering. At an optimum uniaxial pressure of 588 Pa, the piezoelectric and dielectric properties of composites with approximate to41 vol% PZT and soft matrix were K = 230 d(33) = 220 pC/ N, g(33) = 108 mV/m, and d(33)g(33) = 23778 x 10(-15) m(2)/N. The porosity-permittivity relationship was used to determine the depolarizing factor of the composites, which represented the degree of ceramic continuity between electrodes. In general, composites with soft matrix had higher electromechanical properties than those with hard matrix. The effect of poling direction on the piezoelectric and dielectric properties was also investigated. The composites poled along the PZT fibers had higher electromechanical properties than those poled perpendicular to the PZT fibers.