Failure surface development for ABS fused filament fabrication parts

Fused Filament Fabrication (FFF) is the most widely available Additive Manufacturing technology. Offering the possibility of producing complex geometries in a compressed product development cycle and in a plethora of materials, it comes as no surprise that FFF is attractive to multiple industries, including the automotive and aerospace segments. However, the high anisotropy of parts developed through this technique implies that failure prediction is extremely difficult -a requirement that must be satisfied to guarantee the safety of the final user. This work applies a criterion that incorporates stress interactions to define a 3D failure envelope that could prove an invaluable tool in formalizing the embrace of FFF in industry. Tensile, compressive and torsion tests were executed on coupons developed in a traditional FFF printer, as well as a customized, 6-axis robotic printer necessary to produce specimens in out of ordinary orientations. These tests were used to calculate the parameters of the mathematical function that describe the failure envelope. Mechanical tests clearly showed significant difference between tensile, compressive and shear strengths. The calculated envelope shows strong interactions between axial loads, and a considerable interaction between shear stresses and loads applied in directions parallel and perpendicular to the beads.