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Composites with 3-1 connectivity for transducer applications were made by embedding extruded PZT rods in an epoxy matrix. The effects of rod diameter, volume fraction of PZT, and composite thickness on the hydrostatic properties of the cornposites were determined. Due to decoupling of the d3, and dS1 coefficients in a composite with 3-1 connectivity, thedh may be enhanced, even in composites of low volume fractions of PZT. Such composites also-have a low dielectric permittivity. The combination of high dlr values and low E,, value results in a greatly enhanced gh. Composites with 10 vol% PZT were made with values of ah and EL which are, respectively, two times ( S O x C/N) and 25 times (>70 xlO-, (V. m/N) the solid PZT values.

The effect of porosity on the hydrostatic piezoelectric sensitivity was explored for 3–1 composites with a polyurethane matrix. Hydrostatic sensitivity increases rapidly with volume of porosity, and dh increases from 12 x10−12to >200X10‐12 C/N when 40% porosity is incorporated. These composites become strongly nonlinear at >I MPa and consequently would be limited to shallow water operation.