Tribological performance of brake friction materials containing carbon nanotubes

This study examined brake friction materials containing multi-wall carbon nanotubes (CNTs) to determine their effect on the braking performance. The friction materials were produced using conventional dry mixing methods by substituting barite with CNTs (1.7, 4.7, and 8.5 wt.%). Their tribological properties were examined using both a Krauss type tester and a 1/5 scale brake dynamometer. The physical and tribological properties were affected considerably by the CNT content in the friction material. In particular, the CNT-added friction materials showed improved fade resistance and friction stability. Moreover, the CNTs decreased the friction force oscillation during brake application, which was attributed to the increased damping capacity of the friction materials. However, the CNTs decreased the friction effectiveness owing to the lubricating nature of undispersed CNT bundles, and decreased the thermal conductivity of the friction material due to interfacial coupling effects.