Ultrasonic Evaluation of Stiffness Tensor Changes and Associated Anisotropic Damage in a Ceramic Matrix Composite

After describing the crucial role of microcracking in the behavior of ceramic matrix composites, we introduce a phenomenological model in the framework of continuum damage mechanics, where damage is defined as the change of the tensor of elasticity. For damage identification, we have developed a specific ultrasonic device. This immersion set-up was connected to a suitable data processing system for an optimum recovery of the stiffness matrix coefficients from convenient sets of velocity measurements. Linked to a tensile machine, it enabled us to measure the stiffness changes and the anisotropic damage induced by a uniaxial tensile test.