Types of Clutch Facing Materials
I. Material Types and Characteristics Analysis
1. Asbestos-Free Organic Material (AOM)
Core Composition: It takes aramid fibers and polyester fibers as the framework, supplemented by reinforcing materials such as ceramic fibers and potassium titanate whiskers, and is cured with phenolic resin or rubber-based binders.
Performance Advantages:
Friction Stability: The high strength and low creep property of aramid fibers ensure that the friction coefficient fluctuates between 0.3 and 0.4, and the difference between dynamic and static friction coefficients is less than 10%, which effectively reduces shifting impact.
Heat Management Capacity: It can withstand continuous high temperatures of 250-300℃. Air convection heat dissipation is achieved through the pore structure between fibers. Combined with high-temperature resistant binders (such as polyimide-modified resin), the initial temperature of thermal fading is 80℃ higher than that of traditional asbestos materials.
Environmental Protection: It contains no asbestos at all, complying with the EU REACH Regulation, and the VOC emission during the production process is reduced by 40%.
Typical Applications: Passenger car dual-clutch systems (e.g., Volkswagen DSG), manual transmissions of light commercial vehicles.
2. Metal-Enhanced Organic Material (MOM)
Composite Structure: Based on AOM, 5-15% metal components (copper powder, stainless steel fibers, or bronze particles) are added to form a "fiber-metal-resin" three-dimensional network.
Performance Breakthroughs:
Shear Strength: Metal particles fill the gaps between fibers, increasing the shear strength of the material to more than 25MPa, which is suitable for heavy-duty working conditions with torque exceeding 500N・m.
Thermal Conductivity Efficiency: The addition of copper powder increases the thermal conductivity from 0.2W/m・K to 0.8W/m・K, and the attenuation rate of the friction coefficient at high temperatures is reduced by 30%.
Service Life Performance: In the frequent start-stop tests of commercial vehicles, the wear rate is 20% lower than that of AOM, and the service life is extended to 80,000-100,000 kilometers.
Application Scenarios: Heavy-duty trucks (e.g., Volvo FH16), construction machinery transmissions.
3. Ceramic Matrix Composites
Technical Routes:
Alumina Ceramics: With a purity of 92-99.5%, a density of 3.6-3.85g/cm³, and a flexural strength of 300-500MPa, it is suitable for medium loads (≤300N・m).
Silicon Carbide Ceramics: Its thermal conductivity reaches 150W/m・K, it can maintain structural stability at a high temperature of 1400℃, and the friction coefficient fluctuates between 0.35 and 0.45.
Composite Ceramics: Zirconia-toughened alumina (ZTA) combines the advantages of the two above, with a fracture toughness of 8MPa・m¹/² and a 50% improvement in impact resistance.
Limitations: High brittleness (fracture toughness is only 1/10 of that of metals), high processing cost (3-5 times that of AOM), and laser micro-texturing technology is required to improve surface wettability.
High-End Applications: Racing car clutches (e.g., F1 dual-clutch systems), aero-engine starting clutches.
4. Powder Metallurgy Materials
Subtypes:
Copper-Based Alloys: Containing elements such as tin and lead, with a friction coefficient of 0.15-0.25 and excellent corrosion resistance, they are mostly used in wet clutches (e.g., torque converters of automatic transmissions).
Iron-Based Alloys: Reinforced by adding nickel and chromium, with a friction coefficient of 0.2-0.3 and an allowable pressure of up to 3MPa, they are suitable for dry heavy-load scenarios (e.g., mining machinery).
Process Characteristics: A porous structure is formed through sintering at 1000-1200℃, with an oil content of up to 20%, enabling self-lubrication, and the wear rate is 40% lower than that of AOM.
5. Paper-Based Materials
Manufacturing Process: Plant fibers (e.g., sisal) and synthetic fibers (e.g., PET) are interwoven into a web, impregnated with resin, and then hot-pressed into shape, with a density of 0.8-1.2g/cm³.
Performance Characteristics:
Cost Advantage: The material cost is only 1/3 of that of AOM, making it suitable for economical vehicles (e.g., micro-cars).
Friction Characteristics: The porous structure absorbs transmission oil to form a boundary lubricating film, the difference between dynamic and static friction coefficients is less than 5%, and the shifting smoothness is outstanding.
Service Life Shortcoming: The resin is easy to decompose at high temperatures (>150℃), and the wear rate is 50% higher than that of AOM.
