Role of binder in controlling the noise and vibration performance of brake-pads

Although extensive research has been carried out for predicting and mitigating brake noise problems over the past decades, it is still challenging to predict its occurrence due to the complex nature of the brake system. Friction-induced vibration between the tribo couple (i.e. brake disk-pads) is one of the key players for increasing the noise and vibration issues in the brake system. The composition of friction materials (FMs) (i.e. pads/shoes) controls both tribological and noise-vibration (NV) performance. Binder (i.e. resin) is the heart of FMs which binds all the ingredients firmly and provides strength. A lot is reported on the types and amount of resin on the tribological performance, but no study addresses the noise and vibration performance adequately. This work investigates the role of binder in controlling the NV performance of the Cu-free brake-pads. Four types of copper-free brake-pads were developed with varying content (viz., 6, 8, 10, and 12 wt.%) of phenolic resin as a theme ingredient keeping the parent composition fixed. The natural frequencies and damping ratios for the developed pads were evaluated through experimental modal analysis of the pads. The detailed NV performance was evaluated on the in-house developed brake NV test rig by partly following the SAE J 2521 test schedule. Additionally, friction performance was also studied for different braking conditions. Results revealed that the compressibility, porosity, and damping ratio decreased, whereas hardness and natural frequency increased with the increase in resin content in the brake-pads. Overall, among all the pads, the brake-pad with 6 wt.% resin content proved best for the NV performance.