Damage evolution in ceramic matrix composites

The evolution of the matrix cracking spacing in a 0/90 cross ply CAS/SiC ceramic matrix composite has been studied using an interrupted four-point bend test, taking replicas of the tensile surface at several stresses until the saturation cracking stress was reached. A precise strain measurement was simultaneously obtained from a strain gauge fixed on the sample's tensile surface. The interfacial frictional shear resistance to sliding is derived from this data using the ACK model for matrix crack evolution. This is compared with frictional shear stress measurements made by fibre push-down tests, using nanoindentation techniques.