Resistively shunted piezocomposites for passive vibration damping

The results of a theoretical and experimental study of 3-3 coupled resistively shunted piezocomposites are reported. The focus composite material consisted of poled piezoelectric whiskers in an epoxy matrix and was resistively shunted, with the shunt an integral part of the structure. The whiskers were axially poled for 3-3 type coupling. Two types of integral shunts were studied: resistive matrix and thin film resistor. A piezoelectric finite element model was developed to address dynamic behavior for both cases. Modeling results indicate the possibility of large increases in modal damping with some weight penalty. The critical design parameters are piezoelectric volume fraction, shunt resistance, location of piezoelectric whiskers within the structure and geometry. Fabrication and characterization techniques were developed for both shunt types. The use of a filler material to control matrix resistivity (via the percolation effect) also altered dielectric properties considerably. The thin film configuration proved easier to fabricate and the whiskers were poled after composite cure. Measured AW and capacitance values of the composite compared well with theoretical predictions.