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The article explores the ultrasonic welding of lap joints using PEI plates and PEI/CF-fabric prepregs. The authors analyze the structure and mechanical properties of the joints and investigate the impact of different parameters on their formation. They find that the tensile strength of the joints is influenced by the CF-fabric content in the prepregs, with higher content resulting in greater strength. The thickness of the joints also varies depending on the duration of the ultrasonic welding process. The authors conclude that optimizing the parameters can lead to improved functional characteristics of the joints. [Extracted from the article]

The mechanical and tribological properties of polyimide (PI)-based composites loaded with polytetrafluoroethylene (PTFE) and milled carbon fibers (MCF) in the as received and annealed states were studied in order to increase adhesion to the polymer matrix. It has been shown that loading with micron-range MCF (200 μm) doubles elastic modulus of the composites while all other physical and mechanical properties remain at neat PI levels. The three-component composite loaded with annealed MCF and PTFE has possessed the highest wear resistance. In comparison with neat PI, its wear rate has decreased by 312 times for the metal-polymer tribological contact and by 286 times for the ceramic-polymer one. Based on the obtained experimental data, the most preferential conditions for their implementation (load-speed modes for the given types of the tribological contacts) have been determined using a developed computer algorithm. The designed solid-lubricant "PI + 10 wt% PTFE + 10 wt% MCFannealed" composite has been recommended for both metal-polymer and ceramic-polymer tribological units. [ABSTRACT FROM AUTHOR]

The structure and mechanical and tribological properties of composites based on a thermoplastic matrix of polyetheretherketone (PEEK) loaded with carbon fibers of various (nano-, micro and millimeter) sizes were studied. The research is aimed at developing composites applicable for use both in metal–polymer and ceramic–polymer tribojoints, including endoprostheses. It is shown that the surface layer of the PEEK composite loaded with carbon nanofibers can play a damping role in the friction process. This ensures an increased in wear resistance by 1.5–2 times. Carbon fibers of micron and millimeter length play a reinforcing role. Thus, the wear resistance of PEEK composites can be increased up to seven times in metal–polymer tribojoints, while this is reduced by 16 times in ceramic–polymer tribojoints. It is shown that by choosing the type and weight fraction of fiberlike fillers (carbon nano/micro/millimeter fibers) in PEEK matrix, the tribological and mechanical properties can be purposefully increased. This makes it possible to expand areas of application and product range for tribojoints in mechanical engineering and medicine, including those formed using additive technologies. [ABSTRACT FROM AUTHOR]