Friction behavior of innovative carbon friction linings for wet multi-plate clutches

Abstract

The torque transfer capability as well as long-term endurance are essential for wet multi-plate clutches. The quality of the torque transmission process largely depends on the tribological system consisting of friction pairing, lubricant and applied loads. The requirements on friction linings in wet multi-plate clutches increase continuously due to stricter CO2 reduction regulations and the demand of higher power densities.There is a lack of published data and information about the friction behavior of modern Carbon friction linings in wet multi-plate clutch applications, although these friction materials have successfully proven their performance capabilities over the last two decades in synchronizers. Therefore, this article presents results from experimental studies on the friction behavior of innovative Carbon friction linings carried out on a component test rig. Friction screening tests were performed with Carbon-fiber reinforced plastic (CFRP) and Carbon-fiber reinforced Carbon (C/C) linings in brake and constant slip operation. Furthermore, our research included long-term tests with different lubricants (engine/marine/tractor oil).Results show that modern Carbon friction linings can offer advantages over other materials. In the friction screening (brake and constant slip operations) and long-term tests, the torque transfer capability of both friction linings is very stable, even at high specific loads—sliding velocities near 30 m/s and axial pressures of 2.5 MPa. Influences of sliding velocity, pressure and lubricant on the friction performance are presented. Furthermore, the gradient of the Coefficient of Friction (CoF) curve usually decreases at the end of the engagement to enable good control and shift comfort.