Additively Manufactured PLA under static loading: strength/cracking behaviour vs. deposition angle

This paper aims to assess the existing interactions between strength/fracture behaviour and infill angle in additively manufactured PLA subjected to static loading. Plain specimens and samples containing crack-like notches of 3D-printed PLA were manufactured horizontally by making the deposition angle vary from 0° to 90°. A direct inspection of the fracture surfaces revealed that, irrespective of the infill orientation, static failures were caused by two mechanisms, i.e.: (i) initial shear-stress-governed de-bonding between adjacent filaments and subsequent normal-stress-governed breakage of the filaments themselves. The results being generated demonstrate that, from an engineering point of view, the influence of the deposition angle on the overall strength/fracture resistance of additively manufactured PLA can be neglected with little loss of accuracy. The profile of the stress vs. strain curves being obtained experimentally suggests also that the mechanical behaviour of the 3D-printed PLA being investigated can be modelled accurately without requiring the use of complex non-linear material models, with this resulting in a great simplification of the design problem.