Effect of graphite based solid lubricant on noise and braking performance in polymer composite brake friction materials

Purpose This study aims to investigate and evaluate the effects of graphite, used at different ratios as a solid lubricant in brake pads, on both braking/wear performance, a traditional focus, and braking noise, a crucial comfort criterion. Design/methodology/approach In this study, brake pad samples containing graphite at different weight ratios (5%, 10%, 15% and 20%) were developed. The physical properties of these samples were determined. Tribological performance (friction coefficient and wear loss) was determined following the ASTM G99 standard at 50 N load and 10,800 m sliding distance. Sound levels generated during braking were measured in decibels (dB). To investigate the wear mechanisms and surface morphology, the worn surfaces of the samples were analyzed by scanning electron microscopy and energy-dispersive X-ray spectroscopy. Findings According to the research results, increasing graphite addition decreased the coefficient of friction. However, it was observed that the coefficient of friction exhibited a more stable behavior as the graphite content increased. One of the most significant findings was the consistent decrease in average noise level as the graphite content increased. The best performance in terms of wear resistance was observed in the sample containing 5% graphite. Originality/value This study provides a comprehensive approach that examines the effect of graphite used in brake pad formulations on tribological properties and correlates it with noise performance. The findings reveal that a higher graphite content can provide significantly quieter braking at the expense of an acceptable coefficient of friction and wear loss. This provides critical information for brake pad designers to optimize the balance between performance and comfort (noise) and adds value to the literature review.