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Copper has been regarded as one of the indispensable ingredients in the brake friction materials since it provides high thermal diffusivity at the sliding interface. However, the recent regulations against environmentally hazardous ingredients limit the use of copper in the commercial friction material and much effort has been made for the alternatives. In this work, the role of the cuprous ingredients such as copper fiber, copper powder, cupric oxide (CuO), and copper sulfide (CuS) are studied using the friction materials based on commercial formulations. The investigation was performed using a full inertial brake dynamometer and 1/5 scale dynamometer for brake performance and wear test. Results showed that the cuprous ingredients played a crucial role in maintaining the stable friction film at the friction interface, resulting in improved friction stability and reduced aggressiveness against counter disk.

Brake judder caused by corrosion of gray iron disks was investigated. In this study, the microstructure of the gray iron disks and the friction film developed on the disk surface by commercial friction materials were examined to find the root cause of the corrosion induced brake torque variation. Corrosion of the disk was carried out in an environmental chamber, simulating in-vehicle disk corrosion. Moisture content and acidity of the friction materials were also taken into account for this investigation and brake tests to examine torque variation during brake applications were performed using a single-end brake dynamometer. Results showed that the friction film developed on the disk surface strongly affected the amount of corrosion, while graphite morphology of the gray iron had little effect on the corrosion.