Wear of carbon fiber reinforced carbon matrix composites: Study of abrasive, oxidative wear and influence of humidity

The wear of C/C composites has been studied using a subscale aircraft brake dynamometer linked with a mass spectrometer. A disc-on-disc configuration allowed for simulation of various aircraft landing energy conditions (12.5%, 25%, 50%, and 100% of normal landing energy of a Boeing 737 aircraft) performed at 50% and 90% relative humidity levels. The microstructure of composite brakes was altered by applying three different heat treatment temperatures: 1800, 2100, and 2400 C, respectively. A mass spectrometer linked to an environmental chamber of the subscale dynamometer was utilized to measure the in situ CO ₂ release during the wear tests. The relationships between microstructure, hardness of individual components of composites and wear performance at varied conditions are presented. Carbons obtained at higher heat treatment temperatures are most vulnerable to abrasive wear, while the less ordered carbons, typical for samples heat treated at lower temperatures, showed significant amount of oxidative wear. Oxidative wear was related to excessive heating of materials. Optimization of wear behavior of C/C composite is only possible by understanding the mechanisms of the microstructural changes of materials, corresponding mechanical properties and the nature of wear under various environmental conditions.