BRAKE LININGS AND CLUTCH FACINGS

Biake linings and clutch facings consist of friction materials. Friction materials technology encompasses friction material types, their appHcations, friction and wear characteristics, raw materials, manufacturing methods, and evaluation and test methods. 

Brakes and clutches operate both dry and wet. In dry friction couples, the heat is removed by conduction to the surrounding air and stmctural members. Wet friction couples operate within a fluid, usually an oil, which absorbs the heat and maintains the couple at relatively low (below 200°C) temperatures. The fluid also traps the wear debris. 

Requirements. Automotive brakes must satisfy a certain set of consumer expectations, which iacludes safety, comfort, durabiUty, and reasonable cost. In technical terms, these expectations are translated iato a set of specific requirements such as high and stable friction, no or minimal vibration and noise, and low wear rates for the friction material and rotor mating surfaces, all of which have to be achieved simultaneously at a reasonable cost. Particularly, the performance has to be stable under varying appHcation conditions over extremes ia temperature, humidity, speed, and deceleration rate for occasional or many consecutive stops. The requirements for use ia machines are less stringent. 

The preferred descriptive terms for brake or clutch friction materials according to usage are brake pads, used ia disk brakes brake linings, used ia dmm brakes brake segments, used ia medium tmck dmm brakes brake blocks, used ia large tmck dmm brakes and brake disks, used ia large aircraft brakes. Friction materials for clutches are called facings. 

Prior to the mid-1970s, the most common type of friction materials in use in brakes and clutches for normal duty for original equipment installations and for the aftermarket were termed organics. These materials usually contained about 30—40 wt % of organic components and were asbestos-based (3). 

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Friction Materials. Sintered friction materials are classified as metal— nonmetal combinations (49,50). These are best manufactured by the P/M process. Clutch plates, brake bands, brake blocks, and packing compositions are examples of friction materials (see Brake linings and clutch facings). 

Manufacture of friction elements includes the impregnation of fabrics and subsequent lamination, the wet-dough process, and the dry-mix process. Elements from the last two are prepared by compression-molding the formulation for up to an hour at 150—175°C. Thick brake elements require a carefully controUed heating-and-cooHng cycle to minimize stresses created by expansion and contraction (see Brake linings and clutch facings Fillers). 

Brake linings and clutch facings. CNSL and cardanol have found extensive uses in automotive brake... 

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