Abstract
The key goal of this study was to characterize polytetrafluoroethylene (PTFE) based composites with the addition of bronze particles and mineral fibers/particles. The addition of individual fillers was as follows: bronze—30–60 wt.%, glass fibers—15–25 wt.%, coke flakes—25 wt.% and graphite particles—5 wt.%. Both static and dynamic tests were performed and the obtained results were compared with the microscopic structure of the obtained fractures. The research showed that the addition of 60 wt.% bronze and other mineral fillers improved the values obtained in the static compression test and in the case of composites with 25 wt.% glass fibers the increase was about 60%. Fatigue tests have been performed for the compression-compression load up to 100,000 cycles. All tested composites show a significant increase in the modulus as compared to the values obtained in the static compression test. The highest increase in the modulus in the dynamic test was obtained for composites with 25 wt.% of glass fibers (increase by 85%) and 25 wt.% of coke flakes (increase by 77%), while the lowest result was obtained for the lowest content of bronze particles (decrease by 8%). Dynamic tests have shown that composites with “semi-spherical” particles are characterized by the longest service life and a slower fatigue crack propagation rate than in the case of the long glass fibers. In addition, studies have shown that particles with smaller sizes and more spherical shape have a higher ability to dissipate mechanical energy, which allows their use in friction nodes. On the other hand, composites with glass fiber and graphite particles can be successfully used in applications requiring high stiffness with low amplitude vibrations.
Highlights
Today, it can be observed that the interest in advanced composite materials has grown rapidly
Mechanical hysteresis loops were recorded in the force-shortening system, and the computer program calculated the mechanical energy dissipated in each cycle, the secant modulus of elasticity and the value of the average deformation as a function of time
Modifications of highly crystalline fluorine material by pressing with bronze powder, glass fiber and mineral particles are primarily aimed at increasing the thermal conductivity in applications for sliding elements
Summary
It can be observed that the interest in advanced composite materials has grown rapidly. A polymer material with unique properties that is often used in engineering applications is polytetrafluoroethylene (PTFE), more commonly known under the trade name Teflon [1]. It is a hydrofluoric compound with a very stable main chain structure due to strong C–F chemical bonds. Due to the high molecular cohesion of PTFE chains, it is characterized by high chemical/corrosion resistance, low friction coefficient (below 0.1) and has a wide operating temperature range from −260 ◦ C to 260 ◦ C [2]. Modified PTFE is widely used in the automotive, electrical and electronics industries, aerospace, communications, construction, medical devices and implants, blood vessel prostheses, special packaging and protective clothing
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