Tailoring mechanical properties in FFF-printed PEEK/CF scaffolds: The role of fiber content and raster angle

3D-printed Polyetheretherketone (PEEK) /carbon fiber (CF) composites exhibited significant potential for engineering applications. However, existing researches on the mechanical properties had predominantly focused on solid specimens, while investigations into the mechanical behavior of PEEK/CF scaffolds remained limited. In this study, PEEK/CF composites scaffolds with varying CF contents and raster angle were fabricated using fused filament fabrication (FFF) technology. A systematic investigation was conducted to evaluate the effects of CF content and raster angle on the mechanical performance of PEEK/CF composite scaffolds. Tensile testing results revealed that as the CF content increased from 0% to 10%, both tensile modulus and tensile strength initially improved, reaching optimal values at a fiber content of 5%, beyond which further addition led to a decline of mechanics. When the raster angle changed from ±15° to 0/90°, the tensile strength and tensile modulus of PEEK/CF composites reached the optimum at ±75°. Compressive testing demonstrated that the reinforcing effect of CF on compressive modulus and strength was not significant at low raster angles (±15° and ±30°). However, when the raster angle exceeded ±45°, the compressive properties of PEEK/CF scaffold were markedly superior to those of pure PEEK. Furthermore, under identical raster angle conditions, the scaffolds exhibited distinct mechanical responses under tensile and compressive loading. These findings suggest that the internal printing orientation could be strategically tailored according to the anticipated load-bearing requirements of the application for the design and optimization of scaffolds. • Synergistic enhancement of PEEK scaffolds by 5 wt% CF and ±75° raster angle • The tensile strength and modulus of FFF-printed PEEK/CF scaffolds are synergistically maximized at a specific combination of 5 wt% carbon fiber content and a ±75° raster angle. • Raster angle-dependent compressive enhancement in CF/PEEK scaffolds • Carbon fiber reinforcement significantly improves the compressive properties of PEEK scaffolds only when the printing raster angle exceeds ±45°, demonstrating a strong load-path dependent effect. • Energy Absorption Boosted by 285% via Regional Design • A load-adaptive design strategy, which tailors the raster angle in different regions of a PEEK scaffold according to the local stress state, enhances bending energy absorption by 285.3%.