Elastic wave propagation in anisotropic materials

Plane wave propagation in anisotropic media is reviewed starting from the well-known Christoffel equation. The main purpose is to solve the inverse problem which involves an optimal recovery of the complete stiffness matrix from time-of-flight measurements through an immersed plate. It is shown how short ultrasonic pulses can be tracked in and out of principal planes of symmetry from normal modes of the Christoffel equation by a fully computer-assisted device. Experimental results concerning damage assessment in ceramic-ceramic composites under uniaxial loading up to fracture are discussed. A fourth rank damage tensor can be derived from such a complete set of wave speed measurements for each stress level. The evolution versus load of some particular components is characteristic of the void texture and fracture mechanism