Role of different metallic fillers in non-asbestos organic (NAO) friction composites for controlling sensitivity of coefficient of friction to load and speed

Sensitivity of μ (coefficient of friction) of friction composites towards load and speed is composition specific. For an ideal friction material, it should be zero. It was of interest to examine the influence of increasing amount of three commercially popular metallic fillers (steel fiber, brass fiber and copper powder) on the tribological performance of friction composites including sensitivity of μ towards load and speed. Three series of non-asbestos organic (NAO) friction composites comprising of seven composites in the form of brake pads were developed in the laboratory using three metallic fillers as a single variant. All composites were characterized for physical, chemical and mechanical properties. These were further tribo-tested on reduced scale prototype (RSP) for friction, wear and sensitivity of friction coefficient (μ) towards load and speed characteristics. It was concluded that inclusion of metal contents led to enhancement in friction performance of the composites but at the cost of wear resistance, in general. From μ sensitivity point of view, composites with higher metallic contents and hence thermal conductivity (TC) showed better performance. Overall it was observed that copper powder based composite (with 10%) proved as the best performer from both friction and wear point of view.