Resonances in 1-3 piezocomposite rings

Lead zirconate titanate (PZT)/epoxy 1-3 piezocomposite rings with PZT volume fraction φ ranging from 0.58 to 0.93 have been fabricated. They have sufficiently small epoxy width (∼77–81 μm) and can be treated as effective homogeneous media. Stopband resonances (fS1, fS2) can be observed in the spectra and their locations are close to the theoretical predictions. Mode coupling theory and a finite element model (FEM) are applied to estimate the thickness (fT), lateral (fL), radial (fR), and wall-thickness (fW) resonances of the composite rings. As the frequencies and electromechanical coupling coefficients play a significant role in the performance of a 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 observed that the fR and fW vibrations greatly deteriorate at low values of φ. To avoid unwanted modes from coupling to fT, the thickness and aspect ratio of the PZT elements in the rings should be optimized. By using the FEM, effects of the ring dimensions on the lateral resonances can be predicted.