Microstructure and tribological properties of advanced carbon/silicon carbide aircraft brake materials

The structural characteristics of carbon/silicon carbide (C/SiC) aircraft brake materials were studied by means of optical microscopy, SEM, XRD and TEM, and their frictional properties were investigated using a full-size aircraft wheel and brake assembly on a full-scale dynamometer. The materials were composed of layers of non-woven fiber cloth, short fiber web, and needle fibers. SiC and Si were mostly distributed in the short fiber web layers. The SiC matrix consisted of nanosize and micronsize SiC grains. Nano-SiC could help to form the friction film. Micro-SiC could enhance the debris ploughing action to increase the friction resistance. The materials possessed excellent braking performance and wear resistance. The values of friction coefficient under normal landing, overload landing, and rejected take-off dry conditions were 0.27 +/- 0.02, 0.26 +/- 0.01, and 0.24, respectively. It indicated the C/SiC materials with lower fade across the energy spectrum. The average wear rate was about 1.1 x 10(-3) mm/(side-time). The static friction coefficient was about 0.46 +/- 0.05. In particular, the fade ratios of friction coefficient in wet conditions under normal landing and overload landing were about -11% and 8%, respectively, which indicated the friction coefficient of the C/SiC brake materials was influenced slightly in wet conditions. The main wear mechanism was grain-abrasion. (C) 2008 Elsevier Ltd. All rights reserved.