A material length scale-based methodology to assess static strength of notched additively manufactured polylactide (PLA)

The Theory of Critical Distances (TCD) is the name that has been given to a group of design methodologies that all make use of a material length scale parameter to postprocess the local linear-elastic stress fields in the vicinity of the crack initiation locations. The aim of the present investigation is to check whether the simple linear-elastic TCD is successful in predicting static strength of notched components made of 3D-printed polylactide (PLA). PLA is a thermoplastic aliphatic polyester that is produced from renewable biodegradable resources. The accuracy and reliability of the TCD in estimating the static strength of additively manufactured (AM) PLA were assessed against a large number of experimental results generated by testing, under tensile loading as well as under bending, AM notched specimens containing different geometrical features (open notches included). The TCD was seen to be highly accurate, its systematic use resulting in estimates falling mainly within an error interval of about 20%. This result is certainly very relevant since it demonstrates that the linear-elastic TCD can be used successfully to design against static loading notched components of AM PLA by directly postprocessing the results from simple linear-elastic Finite Element (FE) models.