Improved fibre placement in filament-based 3D printing of continuous carbon fibre reinforced thermoplastic composites

This study investigates the mechanism of fibre deposition in conventional 3D printing and presents an aligned fibre deposition (AFD) method to improve the fibre placement. The deposition mechanism reveals that the cracking of the filament in the transition zone and the torsional deformation during the steering path are the main cause of the defects in the conventional printing process. The AFD method is shown to reduce and mitigate the fibre waviness and twisting, hence producing smooth filament deformation, introducing less air voids and fibre breakage during printing. It is found that the AFD method improves the fibre alignment angle from ±25° to ±12° and reduces the void content to 0.27 % during straight-line deposition. During curved-line printing at a large radius of curvature, tow shearing instead of fibre folding is produced by AFD method, resulting in smooth edges with less fibre breakage.