In-plane and out-of-plane quasi-static compression performance enhancement of 3D printed re-entrant diamond auxetic metamaterial with geometrical tuning and fiber reinforcement

Auxetic materials are cellular materials with a unique property of negative Poisson's ratio. The auxeticity and performance of these metamaterials utterly depend on the geometrical parameters and loading direction. For the first time, the quasi-static uniaxial compression performance of fused filament fabricated re-entrant diamond auxetic metamaterial is evaluated in the x-direction (in-plane) and z-direction (out-of-plane). The most commonly used thermoplastic feedstock, Acrylonitrile butadiene styrene, is considered a material of choice. The effect of influential geometrical parameters of the re-entrant diamond structure and printing parameter is systematically studied using Taguchi's design of experiments. Grey-based multi-objective optimisation technique has been adopted to arrive at the optimal structure. Efforts are made to improve the stiffness and strength of the structure with fibre reinforcements. Micro glass fibre reinforcements have enhanced specific strength and stiffness in both in-plane and out-ofplane directions. A sevenfold and thirteen times increase in specific strength and energy absorption is evident for glass fibre-reinforced structures in out-of-plane directions compared to in-plane ones. Proper tuning of geometrical parameters of the re-entrant diamond structure can result in a Poisson's ratio of up to -3.49 when tested in the x-direction. The parametric study has illustrated the tailorability of the structure according to the application requirements. The statistical study has signified each considered parameter's contribution to the compression performance characteristics of the 3D printed re-entrant diamond auxetic metamaterial.& COPY; 2022 China Ordnance Society. Publishing services by Elsevier B.V. on behalf of KeAi Communications Co. Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/ licenses/by-nc-nd/4.0/).