Thermal shock resistance of a 2D-C/SiC composite and its damage mechanisms

The present work investigates the thermal shock properties of a two-dimensional carbon fibre reinforced silicon carbide composite (2D-C/SiC) in air. The 2D-C/SiC specimens were thermally shocked up to 60 cycles between 900 and 300°C. The thermal shock resistance was characterised by the residual ultimate tensile strength (UTS) and interlaminar shear strength (ILSS). The surface morphology and microstructure of the thermally shocked specimens were examined by a scanning electron microscope and an X-ray diffractometer. It is found that ILSS is more sensitive to the damage caused by thermal shock. The composite retains its UTS within 20 thermal shock cycles. However, the ILSS of 2D-C/SiC decreases gradually with increasing thermal shock cycles. The damage mechanisms involve matrix cracking, weakening of the bonding strength of coating/composite and/or fibre/matrix interface, as well as oxidation of PyC interface and carbon fibres.