Stressed oxidation behaviors of SiC matrix composites in combustion environments

Abstract

Performance of three kinds of continuous fiber reinforced SiC matrix composites prepared by chemical vapor infiltration (CVI) method, i.e. 2D C/SiC, 3D C/SiC and 3D SiC/SiC composites, have been investigated in the high temperature combustion environment gas with various creep stresses. The relationship between the life time of composite and the normalized peak strength, defined by the ratio of the test stress to the material strength, was studied. The life time of composites decreased with increasing the normalized peak strength following an exponential relationship. The oxidation resistance of the SiC/SiC composite was the best and that of the 2D C/SiC composite was the worst in the high temperature combustion environment with an applied stress. The experimental results suggested that there was a critical normalized peak strength which controls the oxidation mechanism of C/SiC. Below the critical normalized peak strength, the degradation of C/SiC in the combustion environment was controlled by the diffusion of oxygen and water vapor through the cracks in the composite. Above the critical normalized peak strength, the degradation was controlled by the oxidation of C fibers.