Process-structure–property study of 3D-printed continuous fiber reinforced composites

3D-printed fiber-reinforced composites hold many advantages compared to conventional composites in terms of individualization, mass customization, design freedom, and tailoring the composite geometry to load-bearing specifications. Among candidate continuous fibers for reinforcement, basalt fibers (BFs) serve as an eco-friendly alternative with excellent physical and thermal properties. However, the applicability of continuous BFs to be used for 3D-printed polymer composites was rarely addressed in existing literature. Especially, the effects of impregnation density during manufacturing and the influence of local fiber distribution on the fracture behavior of BF-reinforced composites remain unclear. In this study, a solution coating process was employed as a fiber pre-treatment to improve the packing density of BF in a polylactide (PLA) matrix. The effects of the resulting fiber volume fraction (8–31 %) and the local fiber distribution on the tensile fracture mechanisms of 3D printed BF/PLA samples are thoroughly analyzed using three-dimensional X-ray tomography. It was found that at a concentration of 3 wt%, the coating solution uniformly dispersed optimally between the fibers, resulting in improved impregnation densities of the BF in the PLA matrix. Thus, the resulting composite exhibited a tensile strength of 175 MPa and a Young’s modulus of 6.2 GPa, respectively. A standard linear solid (SLS) model is used for property prediction within a composite design framework to be applied to 3D-printed BF/PLA structures. The model is validated with experimental data from tensile tests. The obtained results demonstrate the applicability of eco-friendly BF/PLA composites for 3D printing of industrial high-performance applications with an individualized property profile.