Lee, P., Lee, L., and Filip, P., "Friction Performance of Eco-Friendly Cu-Free Brake Materials with Geopolymer Matrixes," SAE Int. J. Passeng. Cars - Mech. Syst. 6(3):1389-1397, 2013, doi:10.4271/2013-01-2026.
Besides elimination of copper, the eco-friendly brake materials are developed using geopolymer matrix and natural fibers to replace phenolic resin and synthetic fibers, respectively. The objectives are to diminish i) the amount of volatile organic compounds (VOCs) being released from the brake materials when subjected to temperatures higher than 300 °C; and ii) release the potentially hazardous wear debris particles to the environment. Brake materials were fabricated in university and tested using SAE J2430 test procedure and full scale automotive brake dynamometer (Dyno). Dyno test results indicate that the average friction level of the eco-friendly Cu-free materials (µ ∼ 0.30 to 0.33) was only slightly lower when compared to the baseline material containing Cu (µ ∼ 0.35). All tested materials have passed the Brake Effectiveness Evaluation Procedure (BEEP). The Dyno results show that all tested materials were resistant to thermal fade and the friction level slightly increased with the increased speed in the second effectiveness test. However, the wear rate of the Cu-free materials, as well as the corresponding disc wear, was higher than the wear of Cu-containing baseline material. A thorough SEM/EDX and XRD analyses revealed that the detected friction and wear performance can be ascribed to developed friction layer on surfaces of pad and disc.