PTFE / Kevlar fabric liner type self-lubricating materials, extensively utilized in aircraft, face the challenge of enduring strong ultraviolet (UV) radiation when operating at high altitudes throughout the year. Simultaneously, these self-lubricating joint bearing liner materials, used externally on aircraft, encounter high-intensity friction conditions along with substantial UV exposure. Despite this, there is a paucity of studies focusing on the wear behavior of PTFE / Kevlar fabric liners following UV irradiation. This gap highlights the importance of investigating the impact of intense UV exposure on the wear characteristics of self-lubricating plain bearing liners. In this paper, the UV aging tester model HZ-2008A was employed to subject PTFE / Kevlar fabric liner materials to UV radiation at an intensity of 1 W / m2 2 for varying durations. Post-irradiation, the liner samples underwent reciprocating friction testing using the MXW-01 tester. To examine the macroscopic damage morphology of the abrasion marks on the liner material, a stereo microscope (SM) and a three-dimensional optical profiler (3D-OM) were utilized. Furthermore, the micro-morphology of surface damage and chemical state within the abrasion damage area were analyzed using a field emission scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDS). Reflectance micro-infrared spectroscopy (ATR) was applied to analyze the microstructure of PTFE before and after UV irradiation. The study reveals that the wear behavior of PTFE / Kevlar fabric liners against GCr15 bearing steel balls through 5,000 cycles of reciprocating friction initially decreases and then increases with prolonged UV irradiation. Notably, the liners subjected to short-term irradiation (T=100 T =100 h and 200 h) exhibited the least wear, with the volume of friction loss and the maximum depth of abrasion marks being only two-thirds of those observed in liners that were not irradiated or were irradiated for longer durations (T=300 T =300 h and 500 h). This indicates that UV irradiation's primary impact on the wear performance of self-lubricating spherical bearing liners involves a reduction in PTFE fibers' plastic deformation and their capacity to form transfer films. In comparison to non-irradiated liners, those exposed to short-term irradiation experienced less fiber fracture and formed a "transfer film" that was not sufficiently hard, thus protecting the underlying PTFE fibers from frictional effects. Conversely, extended irradiation resulted in the wear of the surface layer of brittle PTFE fibers, restricting the underlying fibers from undergoing dendritic plastic deformation and limiting the formation of transfer films to small areas. The study further elucidates that the fundamental reason UV irradiation affects the wear performance of the liners is due to changes in the PTFE fibers post-irradiation, such as a decrease in the absorption rate of the- CF 2- group, reduction in molecular weight, decrease in crystallinity, and a transition from ductility to surface layer embrittlement. Consequently, the wear mechanism of the liner material shifts from fatigue and adhesive wear to abrasive wear as irradiation time increases. By irradiating PTFE / Kevlar fabric liner samples without considering the intensity of UV irradiation, the research highlights the significant influence of UV exposure on the wear resistance of PTFE / Kevlar fabric liners, showing a trend of initial decrease followed by an increase in wear damage with extended UV irradiation time. This investigation into the effects of UV irradiation on the tribological properties of self-lubricating PTFE / Kevlar fabric liners for aviation applications is innovative. It extends the understanding of textile material applications in UV-exposed environments and offers insights for material development and process optimization of self-lubricating joint bearing liners. The findings provide a foundation for monitoring the long-term performance of PTFE / Kevlar fabric liner parts in aircraft operating in high-altitude conditions, contributing to the stable operation and maintenance of such aircraft.
