A novel printing strategy to fabricate polyetheretherketone (PEEK)-based composites via hollow filaments filled with multiple reinforcements

Polyetheretherketone (PEEK)-based composites fabricated by material extrusion (ME) have attracted broad research attention; however, the complex pre-made composite filament process makes them inflexible. In this work, a novel composite printing strategy was proposed by filling composite powder into hollow filaments to construct composite filaments for printing. This strategy eliminated the screw extrusion composite filament process and fabricated composite parts directly using composite powders. Hydroxyapatite-reinforced polyetheretherketone (HA-PEEK) and carbon fibre-reinforced polyetheretherketone (CF-PEEK) composite specimens were fabricated based on the proposed printing method, and their chemical, physical, and mechanical properties were investigated. To improve the mechanical performance of the specimens, annealing was conducted. It was found that the printed composite specimens had excellent mechanical properties. The highest flexural strengths of the 10% HA-PEEK-R and 5% CF-PEEK-R specimens were detected as 352.9 and 399.4 MPa, respectively. The compression strengths of the 10% HA-PEEK-R and 20% CF-PEEK-R specimens peaked, representing 123.0 and 137.2 MPa, respectively. Furthermore, adding different functional reinforcement fillers or various filler contents to different segments of hollow filaments, sandwich structures and gradient structures were successfully fabricated.