Enhanced Structural Stability and Interfacial Strength of Thermoplastic Elastomers using Dual Material Bi-layered Filaments by Material Extrusion Additive Manufacturing

While fused filament fabrication (FFF) for soft elastic materials has gained interest, critical challenges need to be addressed for 3d-printing such soft materials. Present technologies within FFF yields poor print resolution, inconsistent print parts, and buckling of filament. This investigation focuses on developing structural integrity and mechanical performance of thermoplastic elastomer (TPE) parts by FFF technique. Proposed approach improves 3D printing characteristics of TPE (shore hardness 75A) by assembling smaller volume fractions of ABS material, to develop core-shell structure of ABS and TPE respectively. Rheological characterizations of feed material using high and low shear viscometry provided an insight about optimizing extrusion parameters for filament production as well as wetting characteristic at the printing interface. Structural integrity of produced filaments was verified by fabricating high precision 3D printed complex benchmark geometries. Izod and 3-point bending test's helped verify that filament geometry was significant for enhancing impact resistance and flexibility of the printed part, owing to its superior interlayer adhesion. Higher volume fractions of TPE exhibited better interlayer adhesion, withstanding mechanical strain of 20% due to its interlayer cohesion. Microstructures of printed geometries under microscope verified good print uniformity of 3D-printed structures with high packing density within adjacent layers. Further investigation includes AFM modulus mapping of print structures to micro-analyze flexibility among soft segments.