High stiffness 3D-printed continuous pitch carbon fiber reinforced polymer composites

This study presents a method for 3D printing very high stiffness pitch-based carbon fiber (CF) reinforced polylactic acid (PLA) composites using a modified open-source 3D printer. The fused filament fabrication (FFF) technique was used to fabricate the samples with alternating layers of PLA and PLA-coated pitch CF. The tensile Young's modulus of the 3D-printed composite samples was measured to characterize the effect of different grades and volume fractions of pitch CF on the behaviour of the printed composites. Three grades of pitch CF which have different Young's modulus were used with volume fractions ranging from 2.4 to 8.4%. Tensile tests showed that the K1392U CF reinforced composite with a 7.3% volume fraction demonstrated the highest improvement in Young's modulus of 850% compared to neat 3D-printed PLA. This improvement is notably higher than any previous 3D-printed carbon-based composites at a relatively low volume fraction of CF. Statistical analysis showed increased Young's modulus in all of 3D-printed composite samples tested. The experimental values were compared to the Halpin-Tsai model and suggest that some degree of fibre breakage occurred during the 3D printing process owing to the relative stiffness of the pitch-based fibers. Future directions and suggestions for process improvements are discussed.