Fatigue strength of a paper-based friction material under shear–compressive loading

Abstract

This paper deals with the fatigue strength of a paper-based friction material under the cyclic shear-compressive loading which is regarded as a real loading condition in an automotive automatic transmission. The paper-based friction material are composed of aramid fibers and phenolic resin. Static fracture and fatigue tests are carried out under various shear and compressive stress conditions. The S-N curves of the paper-based friction material under shear-compressive stresses are described by straight lines in a log-log diagram. The static fracture strength and fatigue strength are higher when the compressive stress is more dominant. The pure compressive cyclic deformation tests are also carried out to explain the fatigue strength of the paper-based friction material under compressive-dominant stress condition. From the tests, it is made clear that with increasing compressive stress, the friction materials becomes dense and the Young's modulus or slope of cyclic stress-strain relation becomes high, and as a result the strain range of the cyclic stress-strain relation remains as constant low value. Therefore, it is considered that the fatigue strength of the paper-based friction material is remarkably high under the compressive-dominant stress condition.