FEM based evaluation of Fused Layer Modelling monolayers in tensile testing

Abstract

In a previous work, dumbbell specimens were shown to be inadequate for the tensile testing of Additive Manufacturing monolayers. Finite Element Method (FEM) has been used in this contribution for comparing tensile-stress distributions in both conventional and rectangular samples. Different extrusion paths for the manufacturing via Fused Layer Modelling (FLM) were taken into account. The calculations showed stress concentrations in the dumbbell type specimens in the zone of variable width away from the gauge length. The results were used for explaining the differences between mechanical behavior of dumbbell and rectangular specimens made with FLM from Poly-Lactic Acid (PLA). The mechanical behavior in the experiments closely matches the FEM results. At least 20 % of the tested dumbbell specimens fractured away from the gauge length, compromising the resulting tensile strength data. Rectangular tensile test specimens are proposed as a better alternative.