Structural transformation of carbon/carbon composites for aircraft brake pairs in the braking process

Amorphous structure discovered from both the wear debris and the friction layer of the carbon/carbon composites after the braking tests was attributed to the breakdown of crystallites in the graphitized bulk material. Graphite layers produced through interlayer shear deformation were found to be the basic units of the pyrocarbon during sliding while carbon fiber tended to be worn into small fragments along the fiber axis in the primary stage of rubbing. The transition of graphitic pyrocarbon in the friction process was described as four stages. Nano-scale carbon particles of onion-like structure were found in the fiction layer, which were likely to participate in the formation of friction layer and lubricate the friction process.