The impact of additive manufacturing induced geometric defects on auxetic lattices

Abstract

While additive manufacturing (AM) has enabled fabrication of intricate features necessary for metamaterials and other lattice structures, it may introduce defects when designs approach the resolution limits of a system. This work examined and quantified the effects of geometric deviations that resulted from AM processes. Reentrant auxetic cells were manufactured at a variety of scales (wall thicknesses of 125–1000 µm) using stereolithography (SLA) and powder bed fusion (PBF). Part inspection revealed a range of small-scale geometric defects, including variation of 20–25 % in the wall thickness when fabricating samples with dimensions approaching the minimum feature size of a printer. Agreement with simulations also grew worse with decreasing sizes, but some defects could be incorporated into the simulations to improve alignment with experiment. Based on these results, it is recommended that the impact of fabrication defects be accounted for when features size approaches approximately 3x the characteristic size of the printing process.