Effect of fiber architectures on thermal cycling damage of C/SiC composites in oxidizing atmosphere

Mechanical response of two and three-dimensional carbon-fiber-reinforced SiC-matrix composites (2D and 3D C/SiCs) subjected simultaneously to thermal cycling and mechanical fatigue in oxidizing atmosphere was compared. Damage was assessed by residual strengths and microstructural characterization. Compared with 2D architecture, the braided 3D composites were shown to possess larger strain increment and strain rate during testing, higher retained strength after 50 thermal cycles, and better damage resistance against oxidation and thermal shock. Differences in oxidation regimes and in thermal shock resistance were ascribed in large part to differences in the fiber architectures. It is actually observed that the fiber architectures have critical influences on the orientations of coating cracking, the constraints between neighboring fiber bundles, and the matrix crack propagating resistance, which can result eventually in the different damage resistance of the composites.