Modeling the Effect of Oxidation on the Creep Behavior of SiC/PyC/SiC Mini-composites Under Wet Oxygen Atmosphere

Abstract

A new model for predicting the creep behavior of SiC/PyC/SiC mini-composites under wet oxygen atmosphere (900 ~ 1200℃, 1% ~ 50%H2O) is developed based on the thermal–mechanical, environmental-micro, fiber strength degradation, and creep-oxidation model. The model firstly takes the effects of the catalysis of water vapor, the oxidation of matrix and interphase, fiber strength degradation due to the grain growing, thermal decomposition, and growth of silica scale, creep of fibers into account comprehensively. The predicted strain–time curves involving three stages presented for the case of a KD-I/PyC/SiC mini-composites are compared to the experimental data at 900℃ under 1%H2O. The model predictions show that the increase of temperature accelerates the consumption of interphase and the growth of silica scale on the fiber, which promotes the failure of fibers by load transfer and fiber degradation. The increase of water vapor pressures promotes the growth of silica scale on the fiber and matrix, but has little influence on the consumption of interphase due to the effect of inhibition of water vapor on the carbon. The effect of creep and oxidation on the matrix crack spacing is checked by the critical matrix strain energy criterion and the results indicate that the creep and oxidation of the mini-composites have no influence on the matrix crack spacing. The application of the method in this work contributes to the analysis of mechanical behavior and failure mechanism of SiCf/SiC structures, such as turbine guide vane, which may serve in the wet oxygen atmosphere for a long period.