Analysis of the resonance modes of PZT/epoxy 1-3 composite rings

PZT/epoxy 1-3 composite rings with PZT volume fractions Φ ranging from 0.58 to 0.93 are fabricated. They have sufficiently small epoxy width (∼77 81 μm) and can be treated as effective homogeneous media. The mode coupling theory and a finite element model (FEM) are applied to predict the thickness (f_T), lateral (f_L), radial (f_R) and wall-thickness (f_W) resonances of the composite rings. As the frequencies and electromechanical coupling coefficients play a significant role in the performance of composite transducer, it is important to know how these parameters change with Φ. Good agreements are found between the experimental results and the FEM simulations. It is obvious that f_R and f_W vibrations greatly deteriorate at low value of Φ. To avoid unwanted modes from coupling to f_T, the thickness and configuration of the PZT elements in the rings should be optimized.