Gap wave propagating in layered piezoelectric material structures with initial stress

In this study, shear horizontal gap waves propagating in layered piezoelectric structures with initial stress is investigated analytically. The boundary conditions imply that the displacement, shear stress, electric potential, and electric displacement are continuous across the interface between the layer and the substrate. The electrically open conditions at the interface between the air and the piezoelectric layer are applied to solve the problem. The phase velocity equation can be obtained and the velocity is numerically calculated and discussed in detail for different initial stresses in the piezoelectric layer. We find that the initial stress has remarkable effect on the phase velocity of the gap waves.