Non-asbestos organic (NAO) friction composites: Role of copper; its shape and amount

A right selection of filler, its type, shape, size, amount and its compatibility with other co-fillers decide the performance of a friction material (FM) at selected operating condition. Amongst various types of metallic fillers, copper is one of the most important fillers used in such multi-ingredient composite system. It not only enhances the thermal conductivity of composite but also plays an important role in friction and wear mechanism. In spite of these facts, in depth systematic studies on investigation role of copper with varying amount and shape and evaluation as per standard procedure are not documented. Hence, in this work investigation on the role of copper (particles and fibers) in FMs were done. Two series of NAO friction composites with varying amount of copper powder and fibers (0, 10 and 20 wt.%) were developed in laboratory. These were characterized for physical, thermo-physical, chemical and mechanical properties. For tribo-evaluation inertia brake-dynamometer testing which reflects the most realistic performance was selected. The various performance properties like friction, wear, μ sensitivity to load, speed and temperature were studied as per industrial schedule. Overall, it was concluded that inclusion of copper improved all major performance properties. From amount point of view, 10 wt.% consider as best amount and from shape point of view, powder has edge on fibers. Worn surface analysis and wear mechanism are also discussed in details.