Interaction of acoustic waves and anisotropic multilayered composite plates immersed in water.

Abstract

In this dissertation a theoretical analysis of elastic wave propagation in multilayered anisotropic composite plates is presented. Reflection and transmission coefficients as a function of the plane wave incident angle and ultrasonic wave frequency are computed for single layered and multilayered plates. From the minima of the reflection spectra one can obtain the Lamb wave modes. Computation of the displacement and stress components inside the plate show that different Lamb wave modes excite different levels of energy at various depths of the plate. These modes can be effectively used to detect and image defects in different layers of a plate. Theoretical predictions have been qualitatively verified experimentally by imaging internal defects inside different layers of a multilayered composite plate by different Lamb wave modes. Numerical precision problems associated with such analyses have been completed avoided for an unidirectional composite plate by solving the problem by symbolic programming instead of conventional numerical matrix manipulation technique.