Fatigue behaviour of additively manufactured polylactide (PLA)

Additive manufacturing (AM) is a group of fabrication techniques through which materials are joined, usually layer upon layer, to make objects from three-dimensional virtual models. Owing to its unique features, this disruptive technology is set to transform the way designers across all engineering disciplines engage with manufacturing. Since this fabrication process affect the way materials behave under static, dynamic and time-variable loading, it is evident that the mechanical performance during in-service operation of AM materials must be studied in depth in order to effectively de-risk their usage in situations of engineering interest. Not only by running appropriate experiments, but also by re-analyzing a number of data sets taken from the literature, the present paper investigates the influence of raster orientation as well as of non-zero mean stresses on the fatigue behavior of AM polylactide (PLA). PLA is biodegradable polymer that can be 3D printed easily and at a relatively low cost. As far as objects are manufacture flat on the build plate, the results being obtained suggest that: (i) the effect of the raster direction can be neglected with little loss of accuracy; (ii) the presence of non-zero mean stresses can be modelled effectively by simply using the maximum stress in the cycle.