Effect of Normal Load and Temperature on the Evolution of Topology of Friction Materials

The friction materials of the drum and disk brakes correspond to one of the most complex materials applied to automotive industry, however, little is known about how this type of material reacts under wear conditions. The aim of this work is to understand the effects of loads and temperatures on the topology of brake's friction materials under wear regime. For this, brake friction material specimens were subjected to wear tests on which procedure was based on the SAE J661 standard. The tests consisted on a sequence of braking and cooling intervals, where friction material specimens were pushed against a rotating drum with controlled velocity. Different test temperatures and normal loads were set. From these tests, the mass loss of each specimen was measured. In order to understand the topological aspects of the materials tested, an optical microscope and confocal microscope were used. The variation of the surface characteristics during the wear process on each specimen was analyzed using quantitative metallography technique and the influences of normal load and temperature on the topology evolution were studied.