Copper-Free Resin-Based Braking Materials: A New Approach for Substituting Copper with Fly-Ash Cenospheres in Composites

Abstract Copper particles emitted from braking have become a significant source of environmental pollution. However, copper plays a crucial role in resin-based braking materials. Developing high-performance braking materials without copper has become a significant challenge. In this paper, the resin-based braking materials were filled with fly-ash cenospheres to develop copper-free braking materials. The effects of fly-ash cenospheres on the physical properties, mechanical and friction and wear properties of braking materials were studied. Furthermore, the wear mechanism of copper-free resin-based braking materials filled with fly-ash cenospheres was discussed. The results indicate that the inclusion of fly-ash cenospheres in the braking materials improved their thermal stability, hardness and impact strength, reduced their density, effectively increased the friction coefficient at medium and high temperatures, and enhanced the heat-fade resistance of the braking materials. The inclusion of fly-ash cenospheres contributed to the formation of surface friction film during the friction process of the braking materials, and facilitated the transition of form from abrasive wear to adhesive wear. At 100–350 ℃, the friction coefficient of the optimal formulation is in the range of 0.57–0.61, and the wear rate is in the range (0.29–0.65) × 10−7 cm3·N−1·m−1, demonstrating excellent resistance to heat-fade and stability in friction coefficient. This research proposes the use of fly-ash cenospheres as a substitute for environmentally harmful and expensive copper in brake materials, which not only improves the performance of braking materials but also reduces their costs.