Research on the fusion of continuous fiber reinforced thermoplastic filaments for fused filament fabrication

The printed continuous fiber reinforced thermoplastic composites have drawn extensive attention due to their excellent mechanical properties. However, interlayer and intralayer voids, which are caused by the insufficient fusion of composite filaments, diminish the mechanical behaviors of the parts. In this work, the influence mechanism of continuous fiber on the fusion process is revealed. A numerical framework based on Lagrangian formulation for simulating the fusion process of pre-impregnated filaments is proposed and verified by experiments. Then, the influence of fiber volume fraction, fiber shape, and fiber eccentricity on the fusion process is studied by the numerical model. The concepts of normalized distance and effective volume fraction are proposed to quantify the influence of the fibers. This study is helpful to further understand the process of filament fusion and void formation in material extrusion additive manufacturing.