Evaluating the tribological and mechanical properties of filament wound composite incorporated with PTFE fibers and tungsten carbide filler applicable for self-lubricating bearings

In this paper, tribological and mechanical features of hybrid E-glass + polytetrafluoroethylene (PTFE)/epoxy and Kevlar + PTFE/epoxy self-lubricating composite bearings with different contents of PTFE yarns were studied. Tribological properties, such as friction coefficient, weight loss, and wear rate, were analyzed by using a linear reciprocating tribometer machine under two loads of 30 N and 40 N. For measuring mechanical characteristics of composite samples, the universal testing machine was applied. To investigate the worn surface and transfer film, a scanning electron microscope (SEM) was employed. EDS elemental analysis was also used to inspect the elemental content of the transfer film. To identify whether chemical changes have occurred in the structure of the composite or not, Fourier transform infrared spectroscopy (FTIR) was utilized. The results showed that composites including 20% glass + 80% PTFE and 20% Kevlar + 80% PTFE exhibited the most effective lubricating performance. The 20% Kevlar + 80% PTFE composite has the lowest friction coefficient, and the transfer film remains more stable during the wear test. Transfer film with a large quantity of 'fluorine' and 'carbon' elements was formed on the surface and led to decrease the friction coefficient. It was concluded that the compressive strength of composite declines with increasing the wt.% of PTFE yarn by investigating the mechanical properties. Moreover, the tribological and mechanical properties of 20% Kevlar + 80% PTFE composites filled with different wt.% of tungsten carbide (WC) (5%, 10%, 20%, and 30%) were studied. Among these composites, the sample filled with 20% WC filler showed superior tribological and mechanical properties compared to other samples.