Structural studies of wear debris from carbon–carbon composite aircraft brakes Original Research Article

Microstructural studies using X-ray diffraction, SEM, and optical microscopy were made of wear debris from carbon–carbon composite aircraft brakes produced under different simulated braking operations. 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 deformation 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 similar disordered 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 temperatures 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.