Experimental characterisation of damage in SiC/SiC minicomposites

Abstract : SiC/SiC composites are studied for their potential use in the next generation of nuclear reactors. A multiscale approach is under development to construct a predictive modelling of their complex damageable mechanical behaviour due to their heterogeneous microstructure. This paper focuses on the damage characterisation of the composite at the scale of the tow at room temperature, both in terms of its spatial distribution and its chronology. Such observations are necessary to validate a multiscale damage modelling at the microscopic scale. The nonlinear behaviour is related to the accumulation of damages such as matrix cracking, fibre/matrix debonding and finally fibre breaking. Therefore, in-situ tensile tests were carried out on SiC/SiC minicomposites using scanning electron microscopy. Specific procedures could be used to get statistical data on the crack evolution. The first results especially show that the growth of the crack openings over the global strain is related to inter-crack distance. This test was complemented by a microtomographic investigation, conducted at the ESRF, performed on a minicomposite submitted to a tensile load. An analysis conducted on the 3D image of a crack shows a slow propagation of the matrix cracking through the minicomposite section.