Effects of hybrid carbon-aramid fiber on performance of non-asbestos organic brake friction composites

The present investigation aims to explore the influence of simultaneous loading of aramid/carbon fibers, as high-performance reinforcements, on thermal, mechanical, and frictional behaviors of phenolic-resin-based nonasbestos organic (NAO) friction materials. The hybrid composite specimens were made at different ratios of carbon and aramid fibers but at a total fixed fiber loading of 8 vol%. The influence of carbon fiber on the improvement of impact strength and thermal conductivity was found to be more prominent than aramid fiber. The thermal stability of friction composites under nitrogen and real condition was investigated. The frictional data drawn from a Chase type friction tester revealed that the coefficient of friction and fade behavior were improved by incorporating aramid fiber. However, carbon fiber improved the wear resistance significantly in comparison with aramid fiber. The surface morphology of the composites was investigated precisely using scanning electron microscopy. Taking all the characterizations (physical, thermal, and tribological) into account, it was revealed that the sample holding 6 vol% aramid fiber and 2 vol% carbon fiber presented the best performance in terms of coefficient of friction, wear rate and fade behavior.