Reza Tavangar - Sahand University if Technology
Hamid Ansari - technology and engineering research center, vehicle engineering research group, standard research institute (SRI), Karaj, iran
Majid Nouri Kamari - Vehicle Engineering Research Group, Research Center of Technology and Engineering, Standard Research Institute, Karaj, Iran

Brake friction composites are required to have a stable tribological behavior under moderate and severe braking conditions. To understand the factors that govern friction behavior, it is necessary to figure out the worn structure in the different conditions. The present study aims to enhance the comprehension of the evolution of pad surface’s micro-structure at different braking applications. For this reason, a commercial copper-free polymer matrix brake pad was tested against a grey cast iron rotor based on the SAE J۶۶۱ standard. Wear surface was studied by scanning electron microscopic (SEM) and an interferometer. Two main regions were observed upon wear surface named high land and low land. High land itself consists of three regions called contact plateaus (primary, secondary type one, and two) and low land which are introduced as micro-slot. The formation of the friction layer strongly depends on the variation of wear structure. A slight change in the worn structure led to variation in friction layer effective parameters which affect the friction coefficient.

Brake pad, wear mechanism, polymer composite, friction layer, wear structure