Performance assessment of aluminum chips in reduced-scale friction for developing copper-free elastomer-modified friction composites

This research paper investigates the frictional and thermomechanical properties of a copper (Cu) free non-asbestos organic (NAO) composite for developing brake friction material for automotive/railway applications. Reduced-scale brake composites were manufactured and tested in a pin on disc tribometer. The effect of aluminum (Al) chips on the dry sliding wear behavior of acrylonitrile-butadiene rubber (NBR) modified phenolic resin-based reduced-scale friction composites was investigated. Other common ingredients of friction materials like fiber, filler, and friction modifiers were not included to get the specific effect of Al on the various properties of the composites. Four composites were prepared with varying Al content, for example, 25, 50, 75, and 100 phr (parts per hundred resins). The average COF increases by ∼70% for 75 phr Al loaded composite (optimum composition) compared to the base composite (devoid of Al). However, mechanical properties, such as hardness and flexure strength, decrease with increasing phr of Al, although compressive strength does not change significantly. The optimum composite exhibits the lowest specific wear rate among Al chips loaded composites. The optimum composite also shows nearly three times improvement in thermal conductivity compared to the base composite. The wear behavior of the composites has been analyzed from the scanning electron microscopy (SEM) images.