Experiments and numerical modeling of dynamic compressive response in auxetic lattices 3D printed from 316L stainless steel

Abstract Auxetic lattices are an important part in the development of smart metamaterials suitable for intelligent applications in high strain-rate dynamics. In this work, three types of auxetic lattices (missing-rib, two- and three-dimensional re-entrant honeycomb) additively manufactured from 316L stainless steel using the LPBF method were subjected to a combined experimental and numerical investigation of their compressive response under quasi-static conditions and during dynamic impact at nominal strain rates of $$1500{\text {s}^{-1}}$$ and $$3000{\text {s}^{-1}}$$ in an in-house designed SHPB apparatus. All the experiments were instrumented using optical cameras for non-contact deformation tracking to establish deformation fields in the samples and calculate the strain and strain-rate dependent function of Poisson’s ratio. A fully 3D three-bar finite element model of the SHPB apparatus and the studied lattices was developed and implemented in LS-DYNA. Mesh density and discretization type sensitivity studies were carried out together with the experimental calibration of strain-rate dependent bilinear constitutive model representing the material of the 3D printed lattices. Simulated dynamic impacts were performed with the same initial conditions as the experiments and the numerical stress-strain characteristics of the studied samples were calculated from the numerical strain signals using the same mathematical methods used for evaluation of laboratory SHPB experiments. The agreement of the experimental and simulated stress-strain response up to the densification region was studied for all the investigated types of lattices at both dynamic strain rates. To interpret the origin of the discrepancies in the simulated and observed stress-strain response as well as the calculated function of Poisson’s ratio, X-ray computed microtomographical imaging was performed and the assessed differences were attributed to the manufacturing inaccuracies and defects in the samples.