This article aims to look into the impact of structural parameters on the tribological, mechanical, and thermal functions of composites. These parameters include the reinforcement type, the winding angle and winding type. The tribological characteristics of polytetrafluoroethylene (PTFE)/epoxy filament wound composites with various reinforcements including E-glass, Kevlar, and ultra-high-molecular weight polyethylene were examined under two different loads and the sliding velocity of 0.12 m/s. After the wear test, the worn surfaces were observed by scanning electron microscopy. The compressive strength of the composites was considered under static loading conditions to investigate the mechanical properties. Also, the thermal conductivity of the composites was investigated. Interfacial shear strength (IFSS) was measured by applying a single fiber microdroplet pullout test. The tribological and mechanical performance of the composites containing Kevlar reinforcement fibers was found to be better than that of PE and glass. The winding angle of 55 showed a better performance, and the hybrid winding type was more suitable than the layered one. So in general, it could be concluded that the hybrid-Kevlar/PTFE-55 composite exhibited the best tribological and mechanical performance among all composites. The thermal conductivity of hybrid-Kevlar/PTFE-55 composites was not high; therefore, it was increased by tungsten carbide (WC). According to the microdroplet test results, IFSS was the highest between Kevlar fibers and the matrix; it was raised by employing WC. The reported results may facilitate the development of self-lubricant composites embedded in WC fillers applicable in bearings.
Self-lubricant composite is a flourish scope of technology that merits academic and industry attention, as it is a specific part which essentially employed in acute operation conditions. In the present study, the mechanical properties of the self-lubricating composite of two-dimensional (2D) and three-dimensional (3D) braid were investigated. The composites contained Polytetrafluoroethylene (PTFE) fibers as a lubricant and glass, carbon, and Kevlar as a reinforcement, hierarchically incorporated into the structure. In order to study the composite behavior as well as to determine the modulus and hardness of the sample, an indentation test, which is very similar in loading to abrasion tests, was applied. A microband test was also conducted to assess the adhesion between the resin and the PTFE fiber. Shear punch tests were performed to evaluate the total shear strength and impact test to estimate energy absorption and impact strength. The results showed that PTFE/epoxy matrix has poor adhesion. Composites with higher PTFE volume fraction had good energy absorption and, at the same time, low shear strength. The higher modulus of carbon composites was concerned.
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.
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