Influence of thermal properties on friction performance of carbon composites

摘要

Three different needled felt C/C composites containing from 5 to 25 fiber oriented normal to the friction surface (z-fiber) were evaluated and tested for friction performance. A laboratory dynamometer was used to simulate cold taxi, hot taxi and normal landing braking events utilizing a sinlge stator and rotor pair. Temperatures measured near the friction surface were lowest for highest thermal diffusivity material demonstrating the effectiveness of z-fiber content at reducing friction surface temperature. Low friction coefficient ((approx) 0.12) under cold taxi conditions increased by a factor of two under hot taxi conditions due to water-desorption transitions. Composites with high diffusivity needed greater braking power to experience transition relative to lower diffusivity materials. Higher braking power was needed to produce a transition under higher humidity conditions. Highest z-fiber content discs showed the lowest wear rate which was attributed to higher in-plane shear strength. The wear rate was highest under hot taxi conditions and it was concluded that mechanisms other than oxidation loss were primarily responsible for the wear of the C/C composites tested in this study. The C/C composite surfaces had a polished appearance suggesting that the removal of nano-scale particles occurs from the friction process.