Oxidation behavior and strength degradation of CVD-SiC coated C/C composites at high temperature in air

Author： Kobayashi Satoshi Wakayama Shuichi Aoki Takuya Hatta Hiroshi

ISSN： 1568-5519

Source： Advanced Composite Materials, Vol.12, Iss.2-3, 2003-06, pp. : 171-183

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Abstract

Simple tensile tests and tensile tests after high temperature exposure of carbon fiber reinforced carbon matrix (C/C) composites have been carried out at high temperature (1000-1400 °C) in air. Types of specimens were bare, notched bare and CVD-SiC coated C/C composites. The CVD-SiC coated C/C composites were mechanically loaded to a strain of 0.13% and were exposed in air at the testing temperature for 10 min. Then, the specimens were subjected to tensile load to failure. The nominal tensile strength of the CVD-SiC coated C/C composite was decreased with increasing temperature due to the oxidation under the coating cracks. Two kinds of true strength were calculated using the cross-sectional area at fracture or the effective cross-sectional area. The effective strength of the CVD-SiC coated C/C composites, based on the decrease in cross-sectional area with no contribution of 90° plies to load carrying, is appropriate to characterize strength after exposure. A diffusion model was applied to predict the oxidation behavior of CVD-SiC coated C/C composite. The effectiveness of the present model was confirmed. It is possible to predict the nominal strength of C/C composites under oxidation condition using the radius of oxidation damage calculated by the diffusion model.