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 th e 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 recover y of the stiffness matrix coefficients from convenient sets of velocit y measurements. Linked to a tensile machine, it enabled us to measure the stiffness changes and the anisotropic damage induced by a uniaxial tensile test.