The many different mechanical parts require many different brake materials. Likewise, the myriad of applications for brakes necessitates variable construction. These devices are used in automotive, railway, transit coach, bicycle, construction machinery and agricultural industries to help control speed and stop vehicles ranging from tractors to race cars. No matter the size or specific part, there are general guidelines for brake materials. These materials must be strong and able to resist wear effects as might be accrued from scoring, galling and ablation. As braking generates a great deal of waste heat, these materials must account for thermal expansion and remain constant at a range of temperatures, have high heat capacity, good thermal properties and conductivity.
These systems inherently deal with a great deal of pressure making the ability to withstand high contact pressures essential to their functionality. Braking systems are often exposed to the environment and must also be able to endure moisture, dust and other environmental factors while continuing to provide consistent slowing capabilities. Many, but not all, components are involved in the creation of friction that leads to the slowing of a vehicle. These particular components must exhibit all of the above characteristics while also maintaining a high coefficient of friction, which is the ratio of the force of friction between two bodies in contact with one another. These friction materials are often rough or textured to provide added friction and increase efficiency.
The basic process of braking relies heavily on the functionality and efficiency of the materials used to manufacture each of the many parts. In braking systems, a lever or pedal is pressed, releasing brake fluid which is put under pressure and delivered to the braking mechanism for each wheel simultaneously. A small hydraulic pump engages the brake shoe or caliper. The shoe presses the pad, or brake lining, into the spinning wheel or disc. The friction created by contact between the two materials causes the wheel to slow in proportion to the amount of pressure applied.
Among the high stress but low friction components such as the brake shoe or caliper, steel, cast iron, aluminum and ceramics are common. While asbestos was once the most popular choice for elements encountering large amounts of friction, health hazards have lead brake production to find alternatives. Ceramic, copper, steel, iron, mineral, cellulose, aramid, chopped glass, rubber and brass are all used in the creation of composite materials used in brakes. These amalgamations are useful in that they retain the qualities, friction resistance and strength, of any and all powders and fibers used in their formation.
These brake materials are often attached via rivets or strong adhesives to metal bases. Field experience, as well as chemical and material engineering, allows constant advancements in brake material design. These advancements result in reduced maintenance and operating costs, longer wear life, better functionality and overall consumer satisfaction.