Characterization of plastic formability and failure mechanisms in FDM additively manufactured PETG and PCL sheets

Abstract

This research work presents an experimental investigation on the formability and failure of additively manufactured polymer sheets. To this regard, Nakajima formability tests following different principal strain paths have been conducted on 2 selected FDM-printed polymer sheet materials, polyethylene terephthalate glycol and polycraprolactone, this being carried out for the first time ever, as far as the plastic behavior and formability study of this kind of 3D printed materials has been limited so far uniquely to conventional tension or compression tests. The analysis includes the evaluation of the different types of failure under plastic deformation for each material considered, allowing the assessment of the overall formability limits within the materials forming limit diagrams combined with the failure evaluation performed via optical microscopy. Thus, the results provided the overall characterization in terms of sheet formability and the comprehensive assessment of the different failure modes and the forming conditions upon which each type of failure is attained for each of the two printed materials. Furthermore, these results allow the authors to create an essential evaluation framework for the ongoing research on process hybridization including the combination of 3D printing technologies with innovative forming processes such as incremental sheet forming.