A bioinspired gradient curved auxetic honeycombs with enhanced energy absorption

Abstract

Traditional auxetic honeycombs often exhibit reduced energy absorption capabilities due to global instability arising from shear band formation, significantly limiting their practical applications. To address this limitation, this study presents the Auxetic Arc-Curved Honeycomb with a novel Bioinspired Layering Gradient (BLG-AACH). The innovative gradient design of the BLG-AACH is inspired by the dense exterior and sparse interior characteristics of biological tissues across multiple scales, utilizing fractal self-similar structure to achieve this biological trait. The BLG-AACH facilitates induced deformation in the intermediate layers, thereby preventing overall global buckling and significantly enhancing energy absorption properties. The compressive behavior of the BLG-AACH was investigated through both experimental testing and finite element modeling. The results demonstrate that the BLG-AACH structure maintains a stable concave folding deformation mode and exhibits multi-level energy absorption capabilities. Its specific energy absorption and total energy absorption are 5.81 and 10.74 times greater than those of the homogeneous AACH, respectively, outperforming other layered configurations. Moreover, the BLG-AACH is highly programmable, enabling the adjustment of mechanical properties such as initial stiffness, plateau stress, and specific energy absorption by varying parameters like cell angle and cell wall thickness. Additionally, Genetic Programming-Symbolic Regression (GP-SR) was innovatively employed to derive a compact and scalable formula for calculating the specific energy absorption of the BLG-AACH, achieving an impressive R² value of 0.99. These findings provide a novel paradigm for enhancing the energy absorption performance and its calculation in auxetic honeycombs.