Structural studies of wear debris from carbon-carbon composite aircraft brakes

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. (C) 1999 Elsevier Science Ltd. All rights reserved.