Microstructural studies using X-ray diffraction, SEM, and optical microscopy were made of wear debris from carbon-carbon composite aircaft brakes produced under different simulated braking operation. Under simulated cold taxiing conditions, particulate wear debris comprising a disordered carbon phase containing fibre fragments is formed. The disordered phase is produced mainly by shear deformaiton of the graphitic CVI matrix in the parent carbon-carbon composite. Under simulated landing conditions the wear debris is partly transformed by shear processes into a friction film with a simila rdisordered microstructure to the wear debris formed during taxiing. The friction film is formed as a result of the higher power density and interfacial temperatures during landing.The very high power densities and interface temperatues that apply during rejected take-off result in shear-stress assisted graphitisation of the friction film, but with a fine mosaic texture that is quite different from the texture of the CVI matrix in the parent composite.
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