A Theoretical study of Propagation of Rayleigh surface waves in functionally graded piezoelectric (FGPM) half-space

This work presents a theoretical study of the propagation behavior of Rayleigh waves in a functionally graded piezoelectric material (FGPM) half-space. The influence of the graded variation of FGPM coefficients on the dispersion curves of Rayleigh waves is investigated for both electrically open and short conditions. The exponential gradient may be applied separately to mechanical and electrical properties. Examples have been given illustrating the use and capabilities of the method based on the recursive stiffness matrix method, in calculating SAW coupling factor (K2) versus crystal orientation, SAW phase velocity for particular frequency range, and field profile variations with depth. The effects of the gradient variation of material constants on the distribution of displacement, stresses and electric potential are presented and discussed in detail. It is note that this paper considers the plane problem of an anisotropic beam which the material composition varies continuously in the direction of the thickness. Some useful discussions and numerical approach are presented to show the significant influence of material inhomogeneity, and adopting a certain value of the inhomogeneity parameter α and applying suitable electric and mechanical loads can optimize the FGPM substrate structures. This will be of particular importance in modern engineering design of high-performance surface acoustic wave (SAW) devices.