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A new successful friction material was developed to operate in the severe high-energy environment of the slipping clutch, including wet start clutch, continuous slip and limited slip applications. The new slipping material was based on the understanding of the interfacial phenomena occurring during the slipping operations. The resulting friction interface (friction material and lubricant combination) possesses the necessary heat dissipation, good shudder resistance and good launch feel. Bench, dynamometer and vehicle test results are presented and the underlying interfacial phenomena are discussed.

A bench test method to evaluate the friction performance for low-speed slip clutch applications such as Electronically Controlled Converter Clutch (ECCC) was developed. Several friction materials were tested against different ATFs at various slip speeds and torque levels. The apply pressure, slip torque output, and torque vibration (shudder) amplitude were monitored while the torque converter clutch was slipping. Two kinds of shudder phenomena, Green Shudder and Long-Term Shudder, were considered. The relationship between torque-speed curve slope and torque vibration amplitude is discussed. The material properties of the friction material candidates were investigated. The results suggest that the developed test method, which measures the amplitude of torque vibration, is a valuable tool for predicting anti-shudder performance. The results also indicate that the torque-speed slope does not have a direct correlation to the torque vibration.

The techniques for characterization of the shear strength of friction materials were reviewed and a new double-lap-shear test method was developed. Various types of friction materials were tested for shear strength by this new technique. The effects of different material properties and processing factors such as resin type, resin content, resin cure rate, fiber geometry, fiber content, and test environment on the shear strength of the friction materials were also examined. Positive correlations between the shear strength and the mechanical life of wet friction materials were established. Accurate determination of shear strength in wet friction materials is vital in predicting the performance and durability of friction materials for friction plates, transmission bands, and torque converter lockup clutches.