Role of thermal conductivity in controlling the tribo-performance of non-asbestos organic brake-pads

The range of thermal conductivity of friction materials is a critical issue since lower thermal conductivity leads to accumulation of frictional heat on the working surface, which results in excessive fade, while higher thermal conductivity leads to excessive heat flow towards back-plate resulting to spongy brakes. Therefore, thermal conductivity of the friction materials across the brake-pads should not be high while along the length of brake-pad; it should be high. To enhance the thermal conductivity, metals in the form of powder or fibres are used in the friction materials. Apart from improvement in thermal conductivity, strength and structural integrity, metals get actively involved in controlling the tribo-performance. Their role as improver of thermal conductivity and hence indirectly tribo-performance can never be known clearly. Keeping this in view, it was proposed to design a bulk of pad rather than the surface. Three types of pads with identical composition but differing in the bulk/body were designed by placing a thin fabric layer of Cu (2 mm away from surface) in one pad and two layers in other pad. The third pad did not contain any fabric. The developed pads were characterized for physical, chemical, thermal, and mechanical properties. Tribo-performance was evaluated on full-scale inertia dynamometer by following the JASO C 406 testing standard. It was concluded that Cu fabric inclusion led to improvement in thermal conductivity and heat exaction capacity, which in turn, improved the tribo-performance of pads significantly.