On the oxidative ablation and mechanical properties of T300 carbon fibers at elevated temperatures

Carbon fibers are the main component and load carrier within many hightemperature composites. Oxidative ablation of carbon fibers is the main failure mechanism of high-temperature composites and significantly affects the mechanical properties of the composites. The effects of the ablation of carbon fiber at high temperatures on carbon fiber mechanical properties, nevertheless, have not been systematically studied in the available literature. In the present investigation, the oxidative ablation behavior of carbon fibers from room temperature to 900°C has been systematically investigated by employing a thermogravimetric analyzer and in situ video detection. Detectable carbon fiber weight loss was initiated when the temperature was elevated to 600°C within the air environment. The video images showed that the color of the carbon fiber surfaces changed dramatically and then the fibers disappeared gradually, indicating that the carbon fibers underwent a chemical reaction, i.e., oxidative ablation. The static mechanical strength of carbon fiber at various temperatures was investigated and was found to start decreasing significantly at temperatures above 500°C, even though no obvious oxidative ablation occurred. X-ray photoelectron spectroscopy (XPS) and Raman spectrum reveal that the microstructure transition from graphite to nongraphite carbon is the main reason for strength reduction.