Impact behavior of auxetic structures: Experimental and numerical analysis

Abstract

Auxetic materials are structured lattice materials with a negative Poisson’s ratio (NPR) and excellent tensile and impact strength compared to conventional bulk materials. It could be used for crashworthy structural applications in aerospace, automotive, and biomedical sections due to its very high specific energy absorption capacity compared to honeycomb structures. With the advent of additive manufacturing technology, it is possible to fabricate complex auxetic structures using metallic, ceramic, and polymeric materials. The literature on the high-speed impact behavior of auxetic structured thermos plastic polylactic acid (PLA) is limited. Therefore, the present work is focused on studying the impact behavior of S-shaped and re-entrant auxetic structures fabricated using Fused Deposition Modeling (FDM). The drop mass impact tests were conducted on these auxetic structures to estimate their impact resistance and energy absorption capability. FEA was undertaken to simulate and validate the impact behavior with experimental results. Quasi-static compression and Split Hopkinson Pressure Bar (SHPB) tests were conducted to get the bulk material's impact properties and material model. These data were used to model material properties in FEA. It was observed that the S-shaped auxetic structure had shown higher compressive plateau stress and energy absorption capacity compared to the re-entrant structure. These auxetic structures' deformation mode and failure were explored through detailed structural analysis using FEA.