The Effect of Fiber Orientation on Lamb Wave Propagation in Layered Anisotropic Composite Plates

Ultrasonic Lamb wave nondestructive evaluation (NDE) is one useful mean to insure the structure integrity of fiber-reinforced composites. In order to take full advantage of the information contained in Lamb wave testing, it is very helpful to have a clear understanding on Lamb wave propagation characteristics in the nondestructive evaluation of these structures or in the analysis of their dynamic vibrations. In this work, a global matrix model is developed based on Nayfeh's transfer matrix technique. The method provides an alternative to the transfer matrix technique and can be used on plate systems of any numbers of layers of different materials and thickness. This study concentrates on the effect of fiber orientation on Lamb wave propagation in layered anisotropic composites plates because plate structures with various degrees of macroscopic anisotropy are often encountered in the study of composite materials. The calculated dispersion curves for various fiber orientations are presented together with plots of the through-thickness particle stress component amplitudes for two fundamental modes a(0) and s(0). These numerical examples provide the rich characteristics of Lamb waves in anisotropic layered plates.