The evolution of brake friction materials: a review
Today, in the fast-moving world, the focus of all automobile companies is to increase the speed of vehicles to reduce travel time. With an increase in the speed of vehicles, there is an urgent need for the development of friction materials suitable for high-speed braking applications. A historical review of various materials used to date for making brake pads and brake drum/disc is done in the present work. Asbestos was the most suitable and widely used brake lining material, but its carcinogenic nature has forced the health and environment agencies to ban it. Ban on the use of asbestos has forced researchers to develop asbestos-free brake friction materials. Today, the non-asbestos organic type of brake pads is most widely used. But, non-asbestos organic type brake pads wear out rapidly and generate lots of wear debris. Wear debris generated from braking materials is a cause of concern to the health and environmental agencies. So, researchers are working on developing environment-friendly brake friction materials for all-weather high-speed braking applications. Natural fibre or agricultural waste-based brake pads are considered as the future material for brake pads. At the same time, cast iron was the most commonly used material for brake discs or drums. Today, various materials such as aluminium matrix composites, carbon-carbon composites, and ceramic-based materials are used to make brake discs or drums. However, the use of cast iron is still preferred. Aluminium matrix composite is considered the future material for brake discs or brake drums because of its low density and improved braking stability.