Material Platform ABS ABS ABS ABS ABS ABS 5% Jute-ABS 5% Jute-ABS 13% GF-ABS/LLDPE^ 18% GF-ABS/LLDPE^ 20% GF-ABS 20% CF-ABS PLA PLA PLA 15% CF-PLA FFF FFF FFF BAAM LSAM FFF FFF FFF FFF BAAM BAAM FFF FFF FFF UTSx 31 MPa 29 MPa 34 MPa 36 MPa 22 MPa 26 MPa 24 MPa 39 kg 59 kg 67 MPa 67 MPa 56 MPa 55 MPa 53 MPa UTSz 6.6 MPa 14 MPa 18 MPa 27 MPa 11 MPa 13 MPa 8.6 MPa 1.2 kg 11 kg 13 MPa 8.2 MPa 24 MPa 37 MPa 35 MPa Table 1. Mechanical anisotropy of extrusion-based printed samples11 INTRODUCTION Fused Filament Fabrication (FFF) is a method of Additive Manufacturing (AM) in which thermoplastic material is extruded through a nozzle to create specific patterns in a plane parallel to the build platform. By sequentially depositing layer upon layer, the printer will build a 3D structure in the Z-Axis (build direction). Due to the consecutive layer printing, the structures typically demonstrate highly anisotropic mechanical properties. The structure is strongest when the deposited beads in the X-Y plane are aligned (0°) with the load direction (X-Y plane). The printed structures are weakest however when the material beads are normal (90°) to one another in successive layers (Z-Axis or build direction), typically seeing a drop from between 40%-85% in ultimate tensile strength.1-3 The anisotropic material properties of the structures can lead to a drop in strength ranging from 25%-97%. Table 1 demonstrates the drop in ultimate tensile strength across the X and Z axis between structures printed on a variety of small scale (FFF) and large (LSAM/BAAM) area additive manufacturing platforms. The material choices for the initial penetrating nozzle research will be neat polymers such as ABS and PLA for their printability. While further work after viability testing will be done with carbon-fiber PLA to compare to prior Z-pinning work. Using ABS, printed structures show www. sampe.org . a drop in strength ranging from 52%-79% across both small area additive manufacturing platforms (FFF) and two large scale platforms such as the big area additive manufacturing (BAAM) platform and the large scale additive manufacturing (LSAM) platform4-9 Reduction Reference 79% 52% 47% 25% 50% 50% 64% 97% 81% 81% 88% 57% 33% 34% 4 5 6 7 8 5 6 9 9 7 7 4 10 10 . Materials printed using neat PLA show a drop in strength ranging from 33%-57% across FFF additive manufacturing platforms, while carbon-fiber PLA demonstrated a 34% drop in ultimate tensile strength4,10 . Several research efforts have attempted to mitigate this drop in ultimate tensile strength. Researchers at University of Wisconsin-Madison developed a custom tool path to control the bead orientation and printed density of the print based on local load direction and stresses. This work resulted in printed parts that achieved an ultimate tensile strength within 3% of traditional, injection molded parts. The weakest parts during this study were the with beads aligned perpendicular to the load direction, reaching only 72% of the injection molded parts strength12 inter-layer bond strength A primary approach for through . Increasing increasing the inter-diffusion of polymer chains across the interface has been another focus of researchers13 . increasing the interlayer bond strength is by actively heating the interface to maintain a temperature above the glass transition temperature of the material13-15 . JULY AUGUST 2022 | SAMPE JOURNAL | 29http://www.sampe.org