Bingli Fan

Tribological Behaviors of PTFE-Based Composites Filled With Nanoscale Lamellar Structure Expanded Graphite

This paper provides a polytetrafluoroethylene (PTFE)/nano-EG solid self-lubricating composite that exhibits very low friction coefficient and wear rate. In present study, the influences of the content of expanded graphite with nanoscale lamellar structure (nano-EG) in PTFE/nano-EG composite, normal contact pressure, and sliding velocity on tribological properties were studied by using the MMU-5G friction and wear tester sliding against AISI-1045 steel. Meanwhile, the property of nano-EG was characterized by utilizing a field emission scanning electron microscope. Compared with that of pure PTFE, the addition of nano-EG into PTFE matrix effectively improved the antifriction and wear resistance properties of PTFE/nano-EG composite. The highest wear resistance was found for the PTFE/nano-EG composite filled with 15 wt % nano-EG. The morphologies of worn surface of the ANSI-1045 steel and composites were observed using a confocal laser scanning microscopy (CLSM) and a scanning electron microscope (SEM) to examine composite microstructures and to study modes of failure. The images of CLSM and SEM indicate that the property of transfer film generated on the surface of mating pair is likely responsible for the lower wear rate observed in these experiments.

Effects of Kevlar® 29 yarn twist on tensile and tribological properties of self-lubricating fabric liner

Yarn twist in textile technology is an important characteristic since it considerably affects the properties of knitted or woven fabrics. Many researchers have investigated the effect of staple-spun yarn twist on the properties of the yarns and fabrics. However, the effects of twist level of Kevlar® 29 filament yarn on the properties of yarn and its resin-impregnated self-lubricating fabric liner are not fully known yet. In this study, we have investigated the effects of Kevlar® 29 twist level on the tensile and tribological properties of the fabric liner (Kevlar® 29/polytetrafluoroethylene fabric-resin composite). Two unexpected findings about the effect of yarn twist have been observed, namely (1) asynchronous twist effect on the yarn’s and the liner’s tensile strength and (2) dissimilar yarn twist effect on the liner’s performance. These findings are mainly attributed to the synergic contributions of the yarn twist and strength and the interaction of the resin with the yarn orientation in the woven fabric structure of the liner.

Influence of 3-aminopropyltriethoxysilane- graphite oxide composite on thermal stability and mechanical property of polyethersulfone

Graphite oxide (GO) was modified using 3-aminopropyltriethoxysilane (APTES) for the fabrication of sheet type APTES–GO composite. Then, this composite was incorporated into the polyethersulfone (PES) matrix to enhance the thermal and mechanical properties of this polymer. The influence of APTES–GO composite on the thermal stability and mechanical property of PES was evaluated. The surface modification of GO by interacting with APTES could be an effective method to improve the compatibility and dispersion of GO sheets within the PES matrix. In comparison with those of virgin PES and GO/PES composites, the thermal decomposition temperature of PES composites containing well-dispersed APTES–GO sheets increased by 18.7°C. The tensile strength, tensile modulus, flexural strength, and flexural modulus of PES composite reinforced with 1.0 wt% APTES–GO sheets were enhanced by 21.1%, 15.2%, 15.4%, and 12.8%, respectively. The enhancement in thermal stability and mechanical property of APTES–GO/PES composite can be attributed to the uniform dispersion of APTES–GO sheets in the PES matrix as well as the strong interfacial interaction between them.

Fatigue failure of 45# steel in dry sliding against Kevlar/PTFE hybrid composite under elevated load

Frictional failure is inevitable for friction pairs. A common sense about the frictional failure of steel-polymer composite friction pair is that the polymer composites are the primary failure part rather than the steel counterpart. However, an opposite case was newly found in the case of fabric self-lubricating liner (Kevlar/PTFE hybrid composite) spherical plain-bearing under elevated load: the steel counterbody suffered a fatigue failure before the fabric composite fails, which resulted in the final failure of the bearing. This paper investigated such fatigue failure of surface chrome plated 45# steel by systematically studying the wear characteristics of 45# steel and fabric composite, the stress distribution of the 45# steel and fatigue features within cross section of the 45# steel. Results showed that wear characteristics of both fabric composite and 45# steel exhibited regional characters. Failure mechanism of the 45# steel was found to be fatigue failure (mainly fatigue pitting), which was revealed by mathematical analysis of the stress distribution of the 45# steel and the fatigue cracks found within subsurface of the cross section of the 45# steel.

Wear Process Analysis of the Polytetrafluoroethylene/Kevlar Twill Fabric Based on the Components’ Distribution Characteristics

Abstract Polytetrafluoroethylene (PTFE)/Kevlar fabric or fabric composites with excellent tribological properties have been considered as important materials used in bearings and bushing, for years. The components’ (PTFE, Kevlar, and the gap between PTFE and Kevlar) distribution of the PTFE/Kevlar fabric is uneven due to the textile structure controlling the wear process and behavior. The components’ area ratio on the worn surface varying with the wear depth was analyzed not only by the wear experiment, but also by the theoretical calculations with our previous wear geometry model. The wear process and behavior of the PTFE/Kevlar twill fabric were investigated under dry sliding conditions against AISI 1045 steel by using a ring-on-plate tribometer. The morphologies of the worn surface were observed by the confocal laser scanning microscopy (CLSM). The wear process of the PTFE/Kevlar twill fabric was divided into five layers according to the distribution characteristics of Kevlar. It showed that the friction coefficients and wear rates changed with the wear depth, the order of the antiwear performance of the previous three layers was Layer III>Layer II>Layer I due to the area ratio variation of PTFE and Kevlar with the wear depth.