A temperature-programmed desorption and oxidation investigation of wear debris from carbon/carbon composite aircraft brakes

Wear debris obtained from pilot scale disc–disc friction tests carried out at different temperatures and sliding speeds were characterized by simultaneous thermogravimetric and mass-spectrometric measurements. The original C/C material consisted of an ex-PAN preform densified by CVI. Friction tests cycles consisted of a large number of identical braking strokes with experimental parameters corresponding to taxiing. Temperature-programmed desorption spectra of CO2, CO and H2O present similarities with those published in the literature for a wide variety of oxidized activated carbons. However the amount of oxygen expressed per unit surface is generally higher for debris than for oxidized activated carbons. The formation of the corresponding oxygen groups is attributed to the mecanochemical actions (rupture, oxidation, and compaction) that carbon debris undergoes on sliding surfaces before being ejected from the disc/disc contact. In addition, temperature-programmed oxidation of debris under diluted oxygen showed that they are much more oxidable than the original C/C material.