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Polymer extrusion three dimensional (3D) printing, such as fused deposition modeling (FDM), has recently garnered attention due to its inherent process flexibility and rapid prototyping capability. Specifically, the addition of electrical components and interconnects into a 3D printing build sequence has received heavy interest for space applications. However, the addition of these components, along with the thermal load associated with space-based applications, may prove problematic for typical thermally insulating 3D printed polymer structures. The work presented here addresses thermally conductive polymer matrix composites (specifically, graphite, carbon fiber, and silver in an acrylonitrile butadiene styrene polymer matrix) to identify the effect of composite geometry and print direction on thermal anisotropic properties. The work also examines the effect of these composites on print quality, mechanical tensile properties, fracture plane analysis, micrograph imaging, and cube satellite thermal analysis. The thermal conductivity of 3D printed material systems in this work may enable the production of thermally stable 3D printed structures, supports, and devices. Key results of this work include anisotropic thermal conductivity for 3D printed structures related to print direction and filler morphology meaning that thermal conductivity can be controlled through a combination of print raster direction and material design. When the materials analyzed in this work are incorporated with other active cooling systems, space-based 3D printed applications can then be designed to incorporate increasing thermal loads, opening a new door to producing space-ready 3D printed structures.

Izod impact test specimens were fabricated via a desktop grade material extrusion 3D printer process using ABS in four build orientations. The 3D printed impact test specimens were examined in order to compare the effect of stress concentrator fabrication on impact test data where two methods were used to fabricate the stress concentrating notch: (1) printing the stress concentrator; and (2) machining the stress concentrator where the dimensions of the notch matched those specified in the ASTM standard D256-10. In both test cases, sensitivity to build orientation was also observed. The sample sets with printed stress concentrators were found to be statistically similar to their counterparts with milled stress concentrators. The experiment was repeated again on a commercial grade material extrusion 3D printer using ABS, PC, PC-ABS, and Ultem 9085 and differences in impact test results were observed most notably when Ultem 9085 was tested. Scanning electron microscopy was utilized to perform fractograpy on impact test specimens to explore the effect of stress concentrator fabrication on the fracture surface morphology of the failed specimens. The work here demonstrates the need for materials testing standards that are specific to additive manufacturing technologies; as well as concluding that all-printed impact test specimens may offer the best representation of the impact characteristics of 3D printed structures.

Material extrusion 3D printing (ME3DP), based on fused deposition modeling (FDM) technology is currently the most widely available 3D printing platform. As is the case with other 3D printing methods, parts fabricated from ME3DP will exhibit physical property anisotropy where build direction has an effect on the mechanical properties of a given part. The work presented in this paper analyzes the effect of physical property-altering additives to acrylonitrile butadiene styrene (ABS) on mechanical property anisotropy. A total of six ABS-based polymer matrix composites and four polymer blends were created and evaluated. Tensile test specimens were printed in two build orientations and the differences in ultimate tensile strength and % elongation at break were compared between the two test sample versions. Fracture surface analysis was performed via scanning electron microscopy (SEM) which gave insight to the failure modes and rheology of the novel material systems as compared to specimens fabricated from the same ABS base resin. Here it was found that a ternary blend of ABS combined with styrene ethylene butadiene styrene (SEBS) and ultra high molecular weight polyethylene (UHMWPE) lowered the mechanical property anisotropy in terms of relative UTS to a difference of 22 ± 2.07% as compared to 47 ± 7.23% for samples printed from ABS. The work here demonstrates the mitigation of a problem associated with 3D printing as a whole through novel materials development and analyzes the effects of adding a wide variety of materials on the physical properties of a thermoplastic base resin.