(221d) Fabrication and Evaluation of Highly Filled Polymer-Based Multi-Layer Filament for Fused Deposition Modeling (FDM)

Applying carbon-based and/or inorganic fillers in 3D printer filaments can enhance the properties of 3D-printed parts and is attracting considerable interest from academic and industry fields. Although 3D-tailored composites have been developed, very little work has been done on the production of advanced filament feedstock for FDM; particularly for highly filled 3D printer filaments that require (i) high filament strength, (ii) high dimensional accuracy, and (iii) superior surface finish. Current FDM filaments rarely exceed filler concentration of 10 wt%, for example, in case of calcium phosphate without sacrificing quality. In this work, a melt-spinning core/sheath die was designed with 2D FEM flow simulations to minimize interfacial flow instabilities; these data were generated based on the die geometry and capillary rheology of ABS and PLA with CaCO₃, which was then compared with the co-extruded filament. With the die, co-axial FDM filament feedstocks of amorphous or semi-crystalline polymer with up to 20 wt% filler concentration have been fabricated. Tensile bars using the filaments were successfully printed with a sufficient surface finish, respectively, and had tensile properties similar to or greater than that of neat filaments. Fracture surfaces of the printed samples after mechanical testing also elucidates the origin of the failure.