Tribological investigation of brake pads

The Anton Paar company has been pioneering frictional tests with the first pin-on-disc tribometer since the 1990s as the requests for controlled friction testing became more and more popular. Bench top tribometer is now a common equipment in many material research laboratories and provide reliable measurement of frictional properties in various areas. One of very important areas of friction is the automotive industry and more specifically the car brakes. The functional part of car brake is the brake disc (rotor) and the brake pad whose purpose is to slow down the vehicle by friction of these two components. The friction between the brake pad and the brake disc must be characterized in order to achieve an optimal braking power. The main factors that influence braking power include the material of both the brake disc and the brake pad, velocity, pressure and environmental conditions (temperature, humidity). The most common material for passenger car brakes rotors is grey cast iron due to its high thermal conductivity. Sports cars use also advanced materials such as ceramic-based composites. The situation with brake pad is very different because its structure is more complex. Generally, the brake pad material is composed of binder, additives, fillers and abrasives that should ensure temperature stability of the coefficient of friction (CoF), low wear and chemical inertness in contact with the brake rotor.