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Material extrusion additive manufacturing provides an effective solution for fabrication of highly customized polyether ether ketone (PEEK) composite parts with any complex shape. Nevertheless, compared with conventional methods, the mechanical strength of 3D printed carbon fiber reinforced PEEK (CF/PEEK) composites is unsatisfactory due to the weak interface bonding strength and high voids content induced by the temperature difference. To overcome this challenge, a temperature‐control 3D printer was used to investigate the effects of ambient temperature and annealing temperature on the microstructure, crystallization behavior and mechanical properties of 3D printed parts. Moreover, the tribological properties of parts printed at different ambient temperature were also studied under various contact pressure. Experimental results showed that the ambient temperature and annealing treatment directly affected the interfacial bonding (fiber/matrix, filament/filament, layer/layer), crystallinity of printed samples, thus affecting their mechanical and tribological properties. The CF/PEEK parts printed at high ambient temperature of 200°C exhibited outstanding mechanical and tribological properties. This study has positive significance for promoting the application of 3D printed PEEK composites in the field of structural load‐bearing and friction materials. Highlights: Structure–property relationships for 3D printed CF/PEEK composites.The ambient temperature strongly affects the thermal and microstructural propertiesInteraction between crystallization and molecular interface diffusion.Interfacial bonding and crystallinity determine the mechanical properties.Tribological properties are highly dependent on applied pressures. [ABSTRACT FROM AUTHOR]

The orientation of fibers in polymer matrix plays a crucial role in governing the performance of composites including friction and wear. In the present work, the effect of fiber orientation on tribological behavior of 3D printed short carbon fiber reinforced PEEK composites (CF/PEEK) was studied by two series of tribo‐tests, namely macro‐scale continuous sliding and micro‐scale multiple scratching. Fiber orientations studied included parallel, tilted and anti‐parallel relative to the sliding direction in both macro sliding and micro scratching. It was revealed that the effect of fiber orientation showed strong dependence on applied loads. In most cases, lower wear were obtained when the fiber orientation was tilted rather than parallel or anti‐parallel in macro continuous sliding. With tilted orientation, the composite also exhibited the best scratching behavior except for that at the lowest normal load. To reveal the mechanisms behind this orientation effects, the composite's worn surface, as well as those of the counter rings, were characterized. Findings of the present work indicates that scratching tests can help understand the macro sliding mechanisms and appropriate fiber orientation is beneficial in improving the tribological properties of polymer composites, which can be realized through 3D printing. Highlights: PEEK composites filled with highly oriented carbon fibers were manufactured by fused deposition modeling (FDM).Tribological anisotropy was studied through macro sliding and micro scratching measurements with respect to carbon fiber orientation.The coupling mechanism of load and fiber orientation was discussed in influencing the composites' friction and wear properties. [ABSTRACT FROM AUTHOR]

Towards the goal of improving the tribological properties of epoxy‐based composites, epoxy resin was firstly modified with carboxyl terminated butadiene acrylonitrile (CTBN), and then further modified by core–shell structured of SiO2@MoS2 fillers. The friction and wear properties of studied composites were tested on a Plate‐on‐Ring configuration under different loads and speeds. To reveal the tribological contribution of MoS2 and SiO2 in the hybrid fillers, tribo‐tests were also done on composites filled with single CTBN, MoS2 and SiO2. It is revealed that the transfer of both the EP/CTBN matrix and SiO2@MoS2 CSs fillers play an important role in governing the tribo‐properties of rubber toughened EP composites. Depending on contacting conditions, the SiO2@MoS2 CSs fillers might be released into the sliding interface and tribo‐chemical reactions might take place, both of which helped improve the tribo‐properties of studied composites. [ABSTRACT FROM AUTHOR]