DESIGN AND DEVELOPMENT OF AUXETIC META-MATERIALS

Abstract

Auxetic structures possess negative Poisson’s ratio due to its unique geometrical configuration. It also offers enhanced indentation resistance, superior energy absorption capacity, excellent impact resistance, and higher compressive strength. In this study, multiple auxetic structures of three novel geometries have been designed by considering different sets of geometric parameters to numerically investigate the mechanical behavior of the structures. The poisson’s ratio, energy absorption and load bearing capabilities have been analyzed trough a numerical model of compression and impact tests. The numerically optimized structures have been fabricated of Acrylonitrile Butadiene Styrene (ABS) using Fused Deposition Modelling (FDM). The fabricated specimens have been subjected to a series of compression, 3-point bending and linear impact tests. Additionally, for the compression test, the simulated results have been experimentally validated. The validation studies have shown very close agreement of their performances with the simulated results. Finally, comparative analyses of energy absorption performances have also been performed to select the most suitable structure. To compare the developed unit cells, initially a series of compression tests were conducted. Through these tests it was observed that Structure-2 exhibits superior performance in terms of maximum loadbearing capacity of 3395 N. On the other hand, Structure-3 has the maximum energy absorption capacity of 51902 N-mm which is 4.85% higher than Structure-1 and Structure-2. For a more definitive analysis, flexural behavior of all the three structures was conducted and based on their results it was established that Structure-2 is the most optimum structure with regard to load bearing and energy absorption capability. This observation has been based on the energy absorption values of Structure-2 analyzed through the all the experimental findings. Structure-2 has been further subjected to a high-speed linear impact test to investigate its performance under high-speed impact loading. It was discovered that after repeated impacts at high speeds, there was no visible damage to the structure thus, maintaining structural integrity, resisting brittle or ductile failure mechanisms, and effectively absorbing and dissipating energy. The comparative findings derived from this study contribute significantly to developing lightweight, energyabsorbent, and impact-resistant auxetic core-sandwiched structures for civil, defence, and automobile sectors.