Effect of internal and external damping in the reduction of non-exhaust particulate matter emissions in a low metallic friction material formulation

Friction -induced vibrations in an automotive braking system are of serious concern, leading to different repercussions. Numerous conventional and unconventional methods have been proposed to curb these vibrations, which are also observed to be directly related to generating non -exhaust particulate matter emissions. In this study, an in-house formulated friction material, tested in the form of pins, was subjected to internal damping by adding rubber content from 0 to 3 wt% and external damping by wrapping the different pins in rubber tape. The DMTA showed a decrease in storage modulus and an increase in loss factor with the increase in rubber content. The pin density decreased with the increase in the rubber content. Dry sliding friction, wear, emissions, and vibrations tests were conducted on a pin on disc tribometer with relevant attachments to measure emissions and vibrations. A large drop in vibrations was observed with the rubber content, irrespective of external damping. On the other hand, a significant reduction in wear, emissions, and vibrations was observed with the sample containing the highest rubber addition and with the damping tape. This study showed the feasibility of employing the combination of internal and external damping, emphasizing the optimum rubber content in friction material formulations.