Friction and wear properties of C/C composite materials under different relative humidities

The friction and wear properties of C/C composites were investigated under different relative humidities on the MM-1000 friction tester.The worn surface morphologies and the dust were observed with a scanning electron microscope.The results show that the friction coefficient and mass loss decrease with increasing relative humidity.Beside,under high relative humidity,because of the lubricating effect of water,the friction coefficient is stabler than that under low relative humidity,and the braking time is very close between them.So,in the actual environment,the level of relative humidity within a short time has little influence on the brakes.However,when the sample is placed in the high relative humidity environment for a long time,the friction and wear properties of materials are greatly affected,it shows long braking time,low friction coefficient and wear mass.By analyzing the worn surface morphologies of material and the debris,the main wear mechanism will be changed with increasing the relative humidity,transforming from oxidation wear under low relative humidity to delamination wear under high relative humidity.