Process optimization of continuous flax fiber/polylactic acid prepreg filaments toward high performance 3D-printed composites

A novel process optimization was proposed by rotational vibration and structural design of flax yarns to manufacture large-tow flax fiber prepreg filaments for 3D printing components with balanced efficiency and performance. It demonstrated that the untwisting of flax yarns generated by rotational vibration produced a dispersed yarn structure, which provided more flow channels for the polylactic acid (PLA) resin to infiltrate yarns. As for the structural design of yarns, the specific surface area increases after replacing the single yarn of large liner density with multiple fine yarns, which further shortens the impregnation time. Unidirectional continuous flax fiber-reinforced thermoplastic (CFRTP) composites were obtained by 3D printing. The mechanical test results showed that the tensile properties of CFRTP composites were significantly increased using filaments consisting of multiple fine flax yarns and the aid of rotational vibration due to the improved impregnation of yarns with PLA resin.