Effects of anti-oxidant migration on friction and wear in carbon-carbon composite aircraft brakes

Carbon/carbon (C/C) composites have been investigated for their application as aircraft brakes since the late 60's. Because of their superior physical, mechanical and thermal properties compared with steel. Currently, C/C brakes are used on almost all military and large domestic aircrafts. One of the major drawbacks of using the C/C brakes is the oxidation that occurs from high temperatures during braking. Many anti-oxidants have been studied and used to provide the oxidation protection on all but the frictional surfaces of the C/C brakes. However, it was noticed that during processing, heat treatment and/or application, some oxidation inhibitors could migrate to the friction surface of the brakes and lead to lower friction effectiveness. In this research, the oxidation protection capability of the phosphorus based oxidation inhibitors was examined. The friction performance of C/C brakes protected by these inhibitors was also investigated and the effects of anti-oxidant migration (AOM) on friction and wear were studied. Also, by using some additives, the phosphorus based inhibitors were modified so that the oxidation protection capability is increased, the migration is lowered and friction performance of the C/C brakes inhibited by the modified anti-oxidant is improved.