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Copper appears to be an indispensable ingredient of non-asbestos organic (NAO) brake friction materials owing to its multifunctionality. However, recent findings proved it as a threat to aquatic life and efforts were initiated worldwide over the last few years to find a substitute for it. Recently, the authors’ group had reported on the potential of particulate Promaxon-D (hydrated calcium silicate), a porous material for enhancement of noise–vibration (NV) performance of Cu-free brake pads. It was felt necessary to investigate how Promaxon-D (PD) contributes to controlling tribo-performance of brake pads since this aspect is most important for the brake friction materials. A series of five types of brake pads was developed by keeping parent composition fixed and varying the theme ingredient PD content from 0–20 wt.%. The tribo-performance was evaluated on a full-scale brake inertia dynamometer as per the JASO C406 test standards. The increase in PD contents led to a reduction in density, hardness, and thermal conductivity while an increase in porosity and compressibility. With the increase in PD contents, almost all tribo properties such as average μ, fade ratio, and recovery ratio got enhanced, sensitivity of µ for pressure, speed, and temperature lowered but at the cost of wear resistance. Finally, the worn surfaces of pads and discs were observed under a scanning electron microscope equipped with energy dispersive X-ray (SEM-EDX) to find out the presence of various elements at the contact zone and to monitor specific topographical events responsible for wear mechanism.

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.

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