Modeling the strength of laminated parts made by fused filament fabrication additive manufacturing

Fused filament fabrication (FFF, also known as fused deposition modeling) is the most popular 3D printing additive manufacturing technology: cheap 3D printers are largely widespread and most polymeric materials can be used. It is probably the most versatile additive manufacturing technology. The applications range from prototyping to the production of custom parts with structural capabilities: fiber reinforced plastics can also be used. However, the knowledge of the FFF materials and the design criteria for fused filament fabricated parts are scarcely known and this results in a very common skepticism in adopting this technology for technical structural components. As for the other processing technologies for plastics, included injection molding, the mechanical properties of the components strongly depend on the manufacturing parameters. As shown by some authors, since production by FFF produces a layered structure, it is possible to model the mechanical behavior by means of the classical lamination theory largely verified and known for composites. In those papers, it was shown that the equivalent elastic properties could be predicted as a function of the lamination stacking and angles. In this paper, based on experimental results obtained on symmetric balanced angle-ply laminated samples made of polyethylene terephthalate with added glycol (PETG) and polyamide (PA) subject to tensile loads, the Tsai-Hill criterion was applied to predict the strength. After identification of the strength parameters, a good correlation of the experimental with the model parameters, for all lamination angles, was obtained.