Experimental and Numerical Investigation of Reinforced Re entrant Auxetic Lattices and a Newly Developed SandWatch Design Using PLA

Abstract

This study explores the physical properties of one auxetic design modification and new developed design inspired by the hourglass, re-entrant honeycomb and the ''SandWatch'', through both experimental testing and finite element analysis (FEA). Baseline and reinforced variants of each design were manufactured with PLA and underwent uniaxial compression testing. Results demonstrated load capability enhancement, energy absorption increase, and auxetic performance enhancement through the addition of wall subdivision in the re-entrant lattice. By contrast, the SandWatch lattices developed a stable stress–strain relationship free of fractures, with the refined version possessing superior stability while the standard design achieving larger auxeticity (NPR ≈ –2.4). FEA accurately reproduced global deformation modes but struggled to capture waviness due to fractures and severe auxetic behavior accurately, while stress errors were within an acceptable range (except one model), the NPR errors remained high. This study's shortcomings comprised effects due to sample storage and simplified boundary conditions. The results emphasize the balance between auxeticity and strength across a range of geometries and reveal how reinforcement techniques can be tailored for optimum application in impact protection and light structural construction.