Effect of friction heat on tribological behaviors of Kevlar fabric composites filled with polytetrafluoroethene

摘要

Friction heat obviously influences the tribological behaviors of Kevlar fabric composites filled with polytetrafluoroethene and thermal fatigue is a key factor to result in wear failure. Especially, when the working temperature of the friction pair is up to a critical value, an abrupt change in tribological behaviors of the braided composites may occur. For reducing and controlling wear of the self-lubricating material, operating conditions applied in braided composites were determined and the tribological behaviors of the Kevlar fabric composites filled with polytetrafluoroethene were investigated under different working temperatures using an oscillatory high load, high-frequency tribo-tester, to study the relationships between temperature and friction and wear. The results show that the friction coefficient of the braided composites is apparently affected by the working temperature, an obvious decrease in friction coefficient occurring with temperature from 10? to 50? and reaching stability with the range from 50? to 130? but having an abrupt change in 140?, while the working temperature also has an evident impact on the wear resistance of the material, with a trend shift in wear of the composites occurring in 140?. In order to maintain good friction and wear behaviors for the braided composites, it is better having the working temperature below 140?. Microscopic analysis of worn surfaces using scanning electron microscope under different working temperatures indicates that the worn surfaces under low working temperature have good lubricating states with not much reinforced fibers exposed, while under high working temperature the local lubrication layers on the friction surfaces peel off and interior fibers are much exposed due to fatigue fracture, resulting in severe wear.