Consumer Fused Filament Fabrication (FFF) desktop 3D printers are used for prototyping, spare parts and even small scale production, but produce parts with lower tensile strength than traditional manufacturing methods. High tensile
continuous fibers increase filament composite strength, but poor fiber adhesion and pull-out are common weaknesses. The few commercially available continuous fiber reinforced (CFR) filaments are costly and only compatible with their manufacturer’s machines.
This work describes the development of a method and a rototype apparatus to produce standardized CFR filament, addressing the weaknesses of CFR thermoplastics while maintaining their compatibility with consumer 3D printers, and thereby achieving mechanical properties required for cost-effective small-scale productions.
A bundle of raw carbon fiber is impregnated with a solution of thermoplastic and compatible solvent, improving the adhesion of the fibers to the thermoplastic and reducing fiber pull-out. The pre-treated fiber is then extrusion-coated with thermoplastic to achieve a standardized filament diameter. 1.75 mm PLA filament reinforced with 12k continuous carbon fiber and per-treated with an ABS- Acetone solution was produced.
Parts and products ranging from small consumer goods to meter- sized airplane wing sections were successfully printed using a standard FFF extruder. Tensile tests showed a yield stress increase of 535% compared to plain PLA, and a 70%
increase compared to filament produced with raw, untreated fibers. Further work is needed to determine the ideal fiber content, its distribution within the filament and the concentration of the solution.