(267g) Enhanced Tunability of Mechanical Properties Using Dual Material Bi-Layered Core-Shell Filaments By Material Extrusion Additive Manufacturing

While FFF technique for soft materials is attracting a lot of researchers due to its advantages as a solvent free processing technique, critical processing challenges need to be addressed for fabricating soft material specimens. Present literature fails to provide a robust solution for good print resolution, repeatability of the printed parts, and buckling of filament as critical processing problems. This work focuses on improving structural integrity and mechanical performance of additively manufactured thermoplastic elastomer (TPE) specimens by FFF technique. This approach focuses on improving 3D printing characteristics of TPE (shore hardness 75A) by assembling smaller volume fractions of ABS material, to develop circular core-shell structure of ABS and TPE respectively. Rheological characterizations of feed material using high and low shear viscometry explains melt flow characteristics during extrusion of core-shell filaments as well as wetting characteristic of print layers. Poiseuille flow is used to understand the extrudability of filaments at printer nozzle. Structural integrity and surface uniformity of produced filaments was verified by developing high precision 3D printed complex benchmark geometries. The izod impact and 3-point bending tests analyze the impact strength and flexibility of print structures at various core-shell ratio to achieve tunability of mechanical properties. Prints at 50% ABS and 62% ABS showcase synergy between flexibility and impact properties to develop high modulus and high strength print structures. Enhanced impact strength is due to superior interlayer adhesion between print layers, increasing the resistance to crack propagation. The fracture surface analysis helps to understand the effect of adhesion in print layers to enhance impact characteristics. Decrease in ABS content results in change of izod specimen failure type from ductile failure to elastic failure. In addition to that, increment in fill density showcases enhancement in mechanical properties on mechanical properties of print structure. Microstructures of printed geometries under microscope verified good print uniformity of 3D-printed structures with high packing density within adjacent layers. AFM modulus mapping of print structures explains the formation of localized high and low modulus segments in print structures, enhancing the mechanical properties of resultant print structures.