Effects of Microscale Texture on the Tribological Behavior of Paper-Based Friction Materials for a Wet Clutch

Abstract

Paper-based friction materials used for wet clutches in automatic transmissions require various tribological functions such as a high and stable friction coefficient, good μ-V (friction coefficient-sliding velocity) characteristics, heat resistance, and wear resistance. In this study, microscale texture was formed on the surface of a paper-based friction material using a picosecond pulse laser, and the friction characteristics were investigated using the SAE#2 test system. Stripe-shaped microtexture (microgrooves) with several patterns of depth and pitch were formed on the friction material surface and controlled by the laser processing conditions. The dynamic friction coefficient was particularly improved by the microgrooves under low temperature and low surface pressure conditions. The coefficient changed according to the depth and pitch of the microgrooves, which is related to the volume ratio (microgroove volume per unit volume of paper-based friction material). These results indicate that the dynamic friction coefficient for the wet clutch can be controlled by changing the groove volume ratio according to the laser processing conditions. A new paper-based friction material with a high static friction coefficient (μs) and good μ-V characteristics could be developed by control of the dynamic friction coefficient without changing the pore characteristics of the paper.

Keywords

• paper-based friction material
• surface texture
• wet clutch