Finite element study of 2-2 piezocomposite transducer with random polymer properties

2-2 piezocomposite materials are widely used for ultrasonic transducers in medical ultrasound imaging and underwater acoustics. An important issue in 2-2 piezocomposite transducer designs is to avoid spurious lateral modes. We proposed a new method to solve the lateral mode problem in this paper. A 30-element 2-2 piezocomposite transducer composed of PZT-5H and five different types of polymers were studied by using ANSYS finite element software. Using a 2-D model of the transducer the electrical admittances were calculated within the interested frequency range. The results show that there is a strong coupling between the thickness mode and the first lateral mode when any one type of polymer is used in the transducer design. However, the lateral mode is greatly suppressed when all of these polymers are used, and the electromechanical coupling coefficient for the thickness mode is also increased. The analysis further shows that the reduction of the lateral mode is only related tothe shear velocity of the polymer, while the density and longitudinal velocity of the polymer have little effect on it.