The Influence of Mullite Shape and Amount on the Tribological Properties of Non-Asbestos Brake Friction Composites

Abstract

For investigating the effect of mullite as a reinforced fiber of the non-asbestos brake friction material on the performance of brake pads, mullite reinforced composites with different contents (5% and 10%) and shapes (powder-based and fiber-based) were developed, and the physical and mechanical properties of the composites were analyzed. The tribological properties of the composites were tested by a Chase tester followed by the IS-2742 standard, and the worn surface was investigated by three-dimensional surface topography and SEM. The results show that the brake friction material with 5% powdered mullite performs best, having the highest stable friction performance (0.86), the lowest wear rate (3%), the lowest friction variation performance (0.263), and the best fade-recovery performance. With the increase of mullite content, the friction variation, wear resistance, and friction stability of the composites become worse. Meanwhile, the performance of powder-based mullite composites is better than that of fiber-based. The worn surface analysis shows that the fiber-based mullite composite has a higher surface roughness, fewer contact platforms, more wear debris, and peeling pits. In contrast, the powder-based mullite composites have a better surface performance. It provides a practical basis for mullite-reinforced non-asbestos brake friction materials.