Effect of FFF process parameters on mechanical strength of CFR-PEEK outputs

Even though Fused Filament Fabrication (FFF) is a widely used additive manufacturing (AM) technology for carbon-fiber-reinforced poly-ether-ether-ketone (CFR-PEEK), the influence of process parameters on print strength has not been comprehensively investigated. In this research, we investigated the influence of three process parameters, namely build orientation, printing speed, and layer thickness, on CFR-PEEK prints’ tensile and compressive strengths through a full-factorial designed experiment. Two designs (i.e., ASTM D695 and ASTM D638) were used to fabricate CFR-PEEK parts in FFF printers. The analysis of variance (ANOVA) test revealed that the main and two-way interaction effects, except the interaction between printing speed and layer thickness, were statistically significant process parameters for tensile strength. The highest tensile strength was achieved at horizontal orientation, lower printing speed, and lower layer thickness. However, the compressive strength of the prints was only impacted by the main effects of build orientation and layer thickness. The combination of vertical orientation, lower printing speed, and lower layer thickness led to the maximum compressive strength. Two general linear prediction models were established to obtain higher tensile and compressive strengths in prints through deriving process parameter settings.