High-performance and geometrically complex parts via co-extrusion additive manufacturing of multi-scale continuous carbon fiber-reinforced thermoplastic composites

Continuous Fiber-Reinforced Polymer Additive Manufacturing (CFRP-AM) often aims to significantly improve the mechanical properties of 3D printed parts. In this paper, we develop a CFRP-AM infrastructure able to print continuous carbon fiber-reinforced polylactic acid (PLA-SCCF) via co-extrusion (i.e., extrusion-based in-situ combination of the thermoplastic matrix and the continuous fibers reinforcement). This infrastructure uses a 6-axis robot to move a co-extrusion printhead over a heated printing bed, and is controlled using a custom-made slicing process. A curved thin-walled vase and a multi-material sandwich panel are made in a single manufacturing step to demonstrate the capabilities of the proposed infrastructure. Their geometrical fidelity is measured and their deviations from the reference model are both < 1%. Micro-computerized tomography scans ( μ CT) are performed to evaluate the micro and meso-structure of printed composite flat beams. Continuous fibers represent ∼ 44 vol.% ( ∼ 58 wt.%) of the composite while voids and porosities represent 0.4 vol.% and 7.9 vol.%, respectively. The ultimate tensile strength (UTS) and stiffness along the principal direction ( E 1 ) are tested for unidirectional flat beams and measured at 854 MPa and 29.5 GPa, representing 16 × and 6.4 × increases when compared to a part reinforced with ∼ 3.4 vol.% ( ∼ 4.5 wt.%) short carbon fibers only, of an average aspect ratio of ∼ 21. The developed co-extrusion CFRP-AM infrastructure could find applications in load-bearing applications where complex part geometries are a requirement, such as the automotive and aerospace industries.