Phenolic-bonded Materials
CAFS Research Area 2 is devoted to the extensive study of brake materials for automotive, heavy duty, and railroad applications. These materials are usually fabricated from a large variety of components and held together with phenolic resin matrix.

Friction Materials for Automotive Brakes
The purpose of any transportation brake system is to convert the kinetic and potential energies of the vehicle into heat within the sliding interface. This system is the number one safety feature of any vehicle.

A brake system consists of two components:
1. actuating system (hydraulic or pneumatic)
2. frictional system (lining or pad, disc or drum)




Disc Brake

Drum Brake

Historical Development of Automotive Brake Materials
• Wood (blocks, leather lining in spoon brakes, band type brakes)
• Metal to metal (iron shoes against steel
• earliest drum stoppers Renault 1903)
• Asbestos reinforced with brass (Frood 1908)
• Sintered iron, copper, brass
• Semi-metallics (polymer matrix – phenolics)
• Non-metallic
• Hybrid (compromising)
• Ceramic (C/C, C/SiC, C/BN, C/B4C) (2000)

Trends
• Higher performance (larger energies dissipated in smaller friction systems; cost, weight and size of braking systems reduced, a more efficient stopping system)

• The coefficient of friction
• Wear rate
• Environmental load
• Noise and vibration
• Chemical species

• Higher stability and reliability (US federal requirement, reduced need for maintenance and repair)
• Shift from trial and error design to science- understanding of principles
• Environmental requirements and limitations

Current Formulation Philosophy
The current formulation philosophy is that low-cost, environmentally-friendly brake materials can be made with good physical properties, adequate and stable friction in a wide range of operating conditions, minimal fade, and high resistance to wear and compatibility with its rubbing counterpart.

Brake Properties and Their Relevance


Disc and Drum Materials
Grey Cast Iron for Rotors and Discs


Cast Iron Chemistry and Hardness
• 2.8 – 3.2 wt.% C
• 1.6 – 1.9 wt.% Si
• 0.6 – 0.8 wt.% Mn
• a maximum of 0.15 wt. % S
• a maximum of 0.3 wt.% P
• CEV = total C % + (P % + Si %)/3 = 3.8 - 3.9 %
• Additional elements possible (carbides, Ti, Cr, Ni)
• HB = 170 – 280
Brake Linings
• Polymer Matrix Composites
• Sintered Metallics
• Ceramics

Brake Lining Materials
At the Center for Advanced Friction Studies, we have examined and tested more than 3000 different materials. A brake lining typically contains 10 to 30 different materials. We have categorized these by the role of the component in the material. These components include:

• Binders
• Reinforcements
• Friction modifiers
• Fillers

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