Humans have always sought to make optimal use of available materials an‎d, inspired by nature, have designed an‎d constructed lattice structures. These structures, due to their low weight, high compressive strength, an‎d stiffness, have found widespread applications in the field of energy absorption. Among them, auxetic structures, as a subset of metamaterials, have gained special attention because of their negative Poisson’s ratio an‎d unique geometry. In this study, a modified re-entrant model with various geometric shapes including square, circular, an‎d elliptical was designed an‎d fabricated. Moreover, foam-filled versions of these models were produced using a 3D printer an‎d additive manufacturing method an‎d were subjected to compression tests. The results showed that filling the structures with foam significantly improved their specific energy absorption performance an‎d resistance to buckling. Among them, the modified model with elliptical geometry exhibited the best performance, with the experimental test showing a maximum specific energy absorption of 273.54 J/kg at a mass of 0.10312 kg, while the numerical simulation predicted 294.66 J/kg at a mass of 0.11 kg, indicating a 7.72% higher prediction by the numerical model. Furthermore, the foam-filled elliptical version, with a mass of 0.12066 kg, achieved a maximum specific energy absorption of 406.23 J/kg in the experimental test an‎d 377.93 J/kg with a mass of 0.126 kg in the numerical simulation, showing a 6.97% lower value in the numerical results compared to the experimental data. These small relative differences indicate the acceptable accuracy of the numerical modeling in predicting the mechanical behavior of auxetic structures. In contrast, the modified models with square an‎d circular geometries demonstrated weaker performance than the elliptical one. In this research, a modified re-entrant auxetic structure with an elliptical geometry an‎d its foam-filled version are presented, both showing superior specific energy absorption an‎d mechanical stability compared to other models. The findings of this study can contribute to the development of metamaterials an‎d the optimization of lattice structures for advanced energy absorption applications.

عليرضا شهيدي ريزي

مسعود عطاپور , سعيد رحمانيان

مهدي جوان بخت , مهدي سلماني تهراني