Frictional performance of C/C-SiC materials at high loads: The role of composition and third-body

Ceramic matrix composites like carbon fiber-reinforced silicon carbon (C/C-SiC) are brake materials for appli-cations at high thermo-mechanical loads. This study investigates the influence of three C/C-SiC pad materials with different compositions on frictional performance. For this purpose, the ceramic pad materials were tested against a steel disk on a dynamometer at brake pressures from 20 to 60 MPa. A large effect due to the different Si and SiC contents of the three pad materials on the frictional behavior was expected. Although the wear rates differed from 40 to 140 mm3/MJ, only marginal differences were found for the coefficient of friction. Hence, additional tests to interrupt and sequence the brake procedure revealed the formation of an intermediate metallic transfer layer from the steel disk on the ceramic pads. The formation and disappearance of this third-body, which was not found in start-complete-stop testing, and the consequences for the frictional properties are discussed.