Relationship between response mechanism of friction coefficient to disc temperature and third body evolution in copper matrix composites

High frictional temperature directly affects braking performance of copper matrix composite (CuMC) brake pads and impose severe thermal shock on brake disc, thereby influencing its service life. Based on a TM-I scaled braking test rig and infrared thermal imaging technology, this study investigates the relationships among coefficient of friction (COF), brake disc temperature, and surface third body at pressures of 0.25–0.75 MPa and initial braking speeds (IBS) of 50–230 km/h. Results indicate that the response relationship between COF and peak temperature is characterized by a temperature threshold of 391 °C, beyond which the two no longer shows mutual response. It can be attributed to the formation and stabilization of an Fe 3 O 4 -containing oxide film at 230 km/h, which promotes the formation of third body layer with high shear strength and adhesion stability, thereby suppressing the dynamic response of instantaneous COF to friction temperature. At 0.25 MPa, when IBS rises from 120 km/h to 200 km/h, COF increases from 0.118 to 0.157, and maximum temperature rise rate increasing from 11 °C/s to 22 °C/s. This study reveals the response mechanism between COF of CuMC pad and brake disc temperature, as well as its relationship with oxidative wear behavior of third body, providing important insights for optimization of friction temperature and development of high-performance brake pads.