An approach to the mechanical behaviour of SiC/SiC and C/SiC ceramic matrix composites

The mechanical behaviour of two woven composites C/SiC and SiC/SiC was investigated at room temperature. The non-linear load-displacement curves and the damaging process were closely related to the specific structure of the composites, consisting of a network of impregnated bundles of fibres. The damage in the bundles proceeded by multiple cracking in the matrix before fibre failure, and dictated the response to the applied load. Other mechanisms, consisting mainly of distortions in bundles and their framework, induced a residual deformation and an energy dissipation. The behaviour was characterized according to the damaging process. Stress-electric strain curves revealed a mechanical response similar to those observed in unidirectional composites, although some effect of the specimen geometry on the curves was observed. Residual strains were similar in tensile and bending conditions. The work of fracture was consistently described by a volumetric rate of energy absorption, related to the applied strain, but the respective contributions of different damage mechanisms could not be determined.