The piezoelectric coupling of 2-2 composite transducers

A field solution is developed to predict dynamic behavior of piezoceramic polymer composite with 2-2 connectivity. The solution is derived based on a concept of Lamb wave propagation along the thickness direction of the 2-2 composite. Dynamic characteristics of various resonant modes are investigated theoretically and experimentally over a broad frequency range. Dispersion curves of the resonant modes are calculated and measured for composites with different ceramic volume fractions. Strong interactions between thickness and lateral resonant modes are observed in transition zones where two resonant modes approach each other. Electromechanical thickness coupling coefficient k_t is evaluated for the first time from a dynamic analysis point of view as a function of ceramic volume fraction as well as the aspect ratio. Results show that the coupling coefficient k_t reaches its maximum value when thickness oscillation is decoupled from lateral modes