Effects of initial stresses on the electromechanical coupling coefficient of SH wave propagation in multilayered PZT-5H structures

The electromechanical coupling factor (K2) presents a key parameter in acoustic devices that reflects the influence of piezoelectricity on the phase velocity of elastic waves. The higher this coefficient, the stronger the dependence of the characteristics of wave propagation on the electric-system parameters. Here, we investigate numerically K2 for third- and fourth-order shear wave modes (SH2 and SH3) in arbitrarily anisotropic multilayered PZT-5H laminates with various orientations. The open-circuit (OC) and short-circuit (SC) are applied to determine this key parameter, while the SH2 and SH3 are chosen because they have a higher K2 in comparison with other SHm modes. Additionally, the effects of initial stresses are taken into account. We find that the initial stress has a significant influence on the SHm (m = 2, 3 modes, especially for thick laminates. The characteristics of SH2 and SH3 modes are analyzed for different thickness ratios of (010)-[100] to (0 - 10 -[100] and periods of PZT-5H layered structures. Results show that K2 varies with the thickness ratio and periods of the laminates. Overall, K2 can reach about 30% and 44% for SH2 and SH3 modes in a laminate with unit thickness ratio and period. Moreover, the sensitivity of K2 to the thickness of the middle layer is discussed in detail. The mechanical stresses, mechanical displacements, electric displacements and electric potentials for SH2 mode are discussed as illustrative examples. Results demonstrate that ([(010)-[100]/(0 - 10 -[100]/(010)-[100])N structures have some useful properties in the design of acoustic wave constructed from piezoelectric materials.