Effects of CVD Carbon on the Erosion Behavior of 5D Carbon-Carbon Composite in a Solid Rocket Motor

An experimental study was conducted to study the effects of chemical vapor deposition (CVD) carbon content on the erosion behavior of 5 direction (5D) carbon-carbon (C/C) composite in a solid rocket motor (SRM). A small SRM, which can compare the erosion performance of two samples under the same working conditions, was designed and tested. The erosion of the carbon-carbon composite ablative morphology at macroscale and microscale was obtained and analyzed. Results show that the average erosion rates of 1# and 2# samples are 0.35 mm/s and 0.45 mm/s, respectively, which means the erosion rate of the sample with high CVD carbon content is 22.2% times lower than the one with low CVD carbon content. During SRM operation, the fibers within fiber bundles and carbon rods are in a dispersive and integral state, respectively, thus carbon rods have a better anti-ablation capability, followed by fiber bundles and matrix in turn. As a result, a carbon rod will be positioned higher than the matrix and fiber bundles around. Furthermore, the ablation of fibers within fiber bundles and carbon rods, although they have significant differences in the ablation process, can both be described as a single fiber ablation. The oxidizing species react with the matrix, then with the CVD carbon and the fiber within a fiber bundle in turn, while they react with the matrix, the CVD carbon and the fiber within a carbon rod simultaneously. This shows that the increase in CVD carbon content will improve the ablation performance of C/C composite by protecting the fibers within the fiber bundles. The present study provides a fundamental understanding of the effect of CVD carbon on the ablation performance of C/C composite, serving as a reference for further design and optimizations of C/C composite.