3D printing with tension and compaction: prevention of fiber waviness in 3D-printed continuous carbon fiber-reinforced thermoplastics

The 3D printing of continuous carbon fiber-reinforced thermoplastics (c-CFRTP) results in fiber waviness and voids that limit mechanical performance. The effects of tensioning and compaction forces during 3D printing were experimentally studied to suppress fiber waviness. A tensioning force was generated along the filament to straighten the fibers by asynchronously controlling the filament feeding and print speeds. A compaction force was applied through the nozzle tip by setting the layer height to reduce the voids. Microscopic images of specimen cross-sections and surfaces indicated a reduction in fiber waviness and voids after these treatments, and three-point bending tests demonstrated improved mechanical properties. This combination of tensioning and compaction forces achieved 28% and 45% higher bending stiffness and strength, respectively. Tensioning and compaction forces are important printing parameters for the 3D printing of high-performance c-CFRTP.