Abstract
Commercially available three-dimensional (3D) printers for continuous-fiber composites feature twin nozzles (one for short fibers (or resin) and the other for continuous fibers). When designers use nonuniformly curved patterns for continuous fibers, inevitable gaps between printing paths cause initial defects. To address this challenge, we developed 3D printer hardware with coaxially arranged nozzles for continuous and short-fiber filaments. This arrangement allows the adjustment of the amount of the short-fiber (or resin) along the continuous-fiber path, preventing print path gaps. The short-fiber nozzle uses a screw and pellets instead of filaments, with a hole at the center of the screw for printing continuous fibers. After modifying the printing conditions, we fabricated unidirectional specimens using the proposed 3D printer and conducted tensile tests, which confirmed its effectiveness for printing continuous-fiber composites.
https://ror.org/0112mx960 
