Sustainable and eco-friendly brake pads: Ensuring reliable copper-free performance with minimal steel fiber

Copper, despite its favorable frictional and thermal properties, poses significant environmental concerns, which necessitate the development of sustainable alternatives. In this study, the tribological performance of low-metallic copper-free brake pads reinforced with steel fibers was investigated using a Chase friction testing machine in accordance with the SAE J661 standard. Low-metallic brake pad friction composites reinforced with 10–30 wt.% steel fibers were fabricated using hot molding as a manufacturing step. The composites were formed under heat and pressure and subsequently post-cured to obtain the final friction materials. The samples were evaluated for normal and hot friction coefficients and wear rate. To evaluate the mechanical integrity of the brake pad composites, shear strength testing was also performed. By eliminating copper and focusing on frictional stability at different temperatures in steel fiber-reinforced formulations, this method enables accurate and reproducible simulation of real-world braking conditions within a controlled laboratory environment. This approach offers a standardized framework for optimizing environmentally friendly friction materials for automotive applications. The results demonstrated that the formulation containing 15 wt.% steel fiber exhibited the most balanced performance, showing a high hot friction coefficient (0.468) and normal friction coefficient of 0.439, indicating consistent friction behavior with low sensitivity to operating conditions, which is regarded as an acceptable coefficient of friction under normal braking conditions. Moreover, this formulation presented the lowest wear rate (4.236%) and excellent thermal stability. These findings indicate that replacing copper with steel fiber reinforcement can maintain reliable frictional performance and durability, offering an environmentally friendly alternative to conventional copper-based brake pads.