Towards optimization of polymer filament tensile test for material extrusion additive manufacturing process

Abstract

Material extrusion (MEX) is a popular additive manufacturing (AM) method that can process a wide range of feedstock materials, most commonly in filament form. Currently, there is no standardized testing method for filament tensile properties, and researchers resort to 3D-printed dog-bone specimens, which necessarily include the effects of the printing process. In this study, the impact of the strain measurement device, knife-edge type, gage length, testing speed, and oven treatment on filament tensile properties was explored using an off-the-shelf fixture. It was observed that an extensometer with blunt knife edges, a filament gage length of 165 mm, and a 6.35 mm/min (0.25 in./min) testing speed could accurately evaluate the tensile properties of acrylonitrile butadiene styrene (ABS) filaments. In addition, an optimized raster path, 3D printing design, and process parameters were used to manufacture dog bone tensile specimens according to ASTM D638-22 from the same ABS filament spool. The tensile properties of the filaments were validated using the results of 3D-printed dog-bone specimens. Young's modulus, stress at yield, and stress at break for the optimum filament test set (2.20 GPa, 43.9 MPa, and 39.1 MPa) were very similar to those of the 3D-printed specimens (2.26 GPa, 44.9 MPa, and 37.3 MPa). The optimum filament tensile testing parameters determined in this study for ABS can be used for the initial test setup for other filament materials to provide baseline values that can serve as the foundation for AM process development.