Q. M. Zhang
Xuecang Geng
Intercollege Mater. Res. Lab., Penn State Univ., University Park, PA 16802
A dynamic model of piezoceramic polymer composites with 2--2 connectivity is presented. It can be used to evaluate the dispersion curves for the thickness resonance and the stop band edge resonance, the effective velocity of the longitudinal wave, as well as the distributions of strain, stress, and the electric field in a composite. Based on these results, the electromechanical coupling factors are determined using two different methods according to the IEEE recommendation. It is shown that the thickness mode coupling factor k[sub t] obtained from the difference of the effective longitudinal velocities at the constant electric field and constant electric displacement is in good agreement with the experimental values. It is also shown that, due to the composite structure, the piezoelectric shear coefficient e[sub 15] has a strong effect on both the effective velocity of the longitudinal wave v[sup D] and k[sub t] even at the limit where the composite thickness is much larger than the period. On the other hand, k[sub t] calculated from the energy consideration is much higher than the experimental values and cannot account correctly for the effect of e[sub 15] on k[sub t]. From the model, the evolution of the thickness mode and the stop band edge resonance with the thickness of a composite and the modes coupling between the two can also be elucidated.