Abstract
Research subject: This study investigates the effect of processed walnut shell Biomass (PNB) on the thermal and tribological performance of eco-friendly brake pads. Since brake pads are safety-critical components, they must provide both thermal stability and wear resistance. Replacing conventional fillers with biomass-based reinforcements such as walnut shell powder offers a sustainable alternative to asbestos while potentially improving overall performance.
Research approach: Brake pad composites were fabricated by incorporating 0–4 wt.% PNB into the base formulation through controlled mixing, molding, and curing. The produced specimens were examined using a combination of analytical and mechanical techniques. Thermogravimetric (TGA) and differential thermal analysis (DTA) were performed to evaluate degradation behavior and char formation. Microstructural characterization was carried out using scanning electron microscopy (SEM) to assess the dispersion of reinforcing particles and the quality of interfacial bonding. In addition, wear resistance and hardness tests were conducted to measure the tribological and mechanical performance of the pads.
Main results: The results revealed a dual effect of PNB addition. Incorporating up to 3 wt.% PNB improved thermal stability, increased char residue, and led to a more uniform microstructure with better particle dispersion. At this composition, surface hardness and wear resistance were also enhanced, while non-uniform wear decreased. However, higher PNB contents (>3 wt.%) resulted in significant deterioration of thermal resistance, formation of porous regions, and weakened interfacial adhesion, causing unstable frictional behavior and lower wear performance. In conclusion, 2-3 wt.% PNB was identified as the optimum composition, ensuring a desirable balance between hardness, wear resistance, and thermal durability.