Effects of porosity on the elastic behaviour of CVI SiC/SiC composites

The purpose of this paper is to deal with the effect of the complex geometry of the porosity of CVI SiC/SiC composites on the elastic behaviour at the scale of the tow, which is an intermediate scale before the modelling of the woven composite. For that purpose, the developed numerical approach consists in the generation of representative micro-structures and in a numerical periodic homogenization procedure for porous materials. As a result, the effective stiffness tensor of the tow is obtained. It will be useful in a further modelling at the upper scale (at scale of the woven composite the tow could be considered as homogeneous). In order to highlight the relevance of this approach, it is compared to a commonly used analytical Mori-Tanaka model. The anisotropy evaluated from the numerical approach is much higher than the anisotropy evaluated from the Mori-Tanaka model. Moreover, this numerical approach is able to evaluate the stress distribution within the composite and especially the high level of stress concentration induced by the complex geometry of the porosity. This high level of stress concentration will have to be taken into account when dealing with the initiation of damage within the composite.