Development of 1-3 PZT-polymer composite for low frequency acoustical applications

Piezoelectric 1.3 composites of PZT-epoxy and PZT-polyurethane compositions were developed for investigations in low-frequency acoustic applications. Samples with different PZT volume fractions and varying PZT rod aspect ratios (from 4/spl times/4/spl times/9 to 1/spl times/1/spl times/9 mm/sup 3/) were fabricated by using the "dice and fill" method. Experimental measurement in the 3.3 mode in air was carried out by using a laser-Doppler vibrometry (LDV) technique. Strain profiles of the composite sample driven by a low-frequency ac electric field excitation was obtained. The result showed that PZT rod aspect ratio has a drastic effect on composite performance. A quasi-static model based on an isolated 1.3 composite unit-cell was developed to account for the stress transfer at the PZT-polymer interface. Analysis result showed that an aspect ratio of 20 or higher is necessary for low frequency sensing or projecting application of 1.3 piezocomposites. For use in the 3.3 mode, a soft polymer was shown to be preferred, since the longitudinal clamping of the PZT rod is greater for hard resins.