Elastic wave propagation in multilayered anisotropic media with applications to composite

An efficient recursive algorithm, the stiffness matrix method, has been developed for wave propagation in multilayered generally-anisotropic media. This algorithm has the computational efficiency and simplicity of the standard transfer matrix method and is unconditionally computationally stable for high frequency and layer thickness. This algorithm is easily adoptable for laminates with periodicity, such as multi-angle lay-up composites. Based on this method, characteristic equations for Lamb and surface waves have been obtained. Analytical formulations for layer stiffness matrix also obtained for isotropic and aniostropic material in plane of symmetry. These formulations are as simple as these for transfer matrix.; A dynamic homogenization method based on Floquet wave theory is developed. The theory is based on the equivalence within the homogenization domain of Floquet waves in a periodic medium and plane waves in a dispersive homogeneous anisotropic medium. Based on this theory, an inversion method to determine the lamina elastic moduli of a cross-ply composite from ultrasonic time-delay measurement has been introduced. This method is based on the Floquet wave velocity measurement in a periodic medium within the homogenization zone and lamina properties reconstruction from this velocity.; The phenomena of wave transmission through a cross-ply composite immersed in fluid have been investigated. The experimental and theoretical results show that the transmission amplitude is highly dependent on ply orientation and angle of incidence at frequency 2.5MHz. Transmission phenomena have been interpreted in terms of Floquet wave, Lamb wave and fluid loading effects.; The time-domain response of a line focus acoustic microscopy from a composite plate have also been studied. A model based on a recursive stiffness matrix method for a multilayered composite is developed and applied to interpretation of the time-resolved acoustic microscopy signature. The applicability of the time resolved acoustic microscopy signature for determination of elastic constants of a unidirectional composite or one lamina in a cross-ply composite has been demonstrated.