The idea of using composites reinforced with hybrid components that simultaneously have the desired strength and wear properties, has become very popular today in various industries. There are many composites in the industry such as gears, bushings, bearings and slide plates that are subjected to high wear and friction. Therefore, these components need to be lubricated to prevent wear between them and to reduce the friction coefficient. Polytetrafluoroethylene (PTFE) has the lowest friction and therefore the highest lubricity. However, due to its poor mechanical properties and high wear rate, this material is usually used in combination with other materials to improve its mechanical properties, wear and even thermal stability. Because PTFE fibers show low wear resistance, PTFE / reinforcement hybrid composites offer a combination of high wear resistance and a low friction coefficient. In this thesis, a hybrid composite is designed and produced to provide self-lubricating properties and at the same time with low friction and wear to strengthen epoxy resin. Hence, the PTFE component was used as a friction reducing agent and the reinforcing component was used as a wear-resistant element. This hybrid composite was produced by filament winding method and consists of two different yarn components, one of which is PTFE and the other is a reinforcement yarn. First, the effect of the percentage of PTFE yarn on the tribological properties of the composite was eva‎luated and the optimal percentage was selected. Then, composite samples were produced using the optimal percentage of poly-tetrafluoroethylene yarn and three different structural parameters, each with several levels, which are: winding type in two levels: in the first type, arrangement of PTFE / reinforcement component was considered as a layer; The arrangement is such that the first layer is made of PTFE and the next layer is reinforcement. The second type is hybrid that PTFE and reinforcement yarns were wrapped in a multi-stranded yarn on the mandrel and then cured. The second parameter is the type of reinforcement yarn (glass, Kevlar, ultra-high molecular weight polyethylene), and the third parameter is the winding angle (three angles of 55º, 70º and 82º). In this study, tribological, mechanical and thermal properties of produced composites were investigated. Furthermore, in the winding stage during composite production, tungsten carbide powder (WC) and multi wall carbon nanotubes (CNTs) were added to the epoxy resin with the aim of increasing tribological, mechanical properties and thermal conductivity of the composite. Tribological, mechanical and thermal properties of 20% Kevlar+ 80% PTFE composites that reinforced with different percentages of WC (5%, 10%, 20% and 30%) and CNTs (1%, 3% and 5%) were studied. The interfacial shear strength (IFSS) properties of fibers and resin were also investigated. The morphology of the composite surfaces after wear were also eva‎luated by scanning electron microscopy (SEM). X-ray energy diffraction (EDS) spectroscopy was also used to investigate components in the transfer film. In order to eva‎luate properties of composites, calculation of friction coefficient and thermal conductivity were theoretically calculated. The results showed that 20% Kevlar+ 80% PTFE composite is the optimal sample in terms of friction coefficient and wear rate. Tribological, mechanical and thermal properties have also been improved by adding 20% WC and 3% CNTs. In the optimal case, the friction coefficient reached to 0.028 and the wear rate reached to 1.32×10-7 cm3/N.m. Also, the highest thermal conductivity is 2.752 W/mK. The highest IFSS was also obtained between epoxy resin reinforced with CNTs and Kevlar fibers.

مهدي حجازي

ابوذر طاهري زاده

مهدي صالحي، محمد شيخ زاده، هوشنگ نصرتي