Engineering Properties of Drum Brake Friction Materials

The rising popularity of EVs has led to a resurgence of interest in drum brakes. Drum brakes benefit from less complex mechanical design, have no residual brake drag, and the enclosed design is less susceptible to corrosion and debris emission. For the commercial EVs, the elimination of engine noise makes brake noise a major contributor to vehicle noise. With the renewed interest in drum brakes, there is an increased need for property data for NVH simulations to optimize noise performance. Similar to disc brakes, the modeling of drum brake performance requires a complete set of friction material engineering properties determined over the pre-loads and temperatures encountered in brake applications. Results are presented for eight different drum brake formulations and platforms. The measurement approach and data analysis parallels that used for the elastic property measurements of disc pad friction materials, SAE J2725. A complete set of elastic properties and engineer properties are measured on several formulations over the temperature range from 20°C to 325°C and pre-loads from 5 bar to 30 bar. These drum brake friction material elastic properties are compared with those typically encountered in disc pads. The sample preparation techniques, data collection methods, and analysis procedures used to mitigate the influence of drum brake curvature will be described.