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Negative Poisson's ratio honeycombs have been widely studied in recent years due to their unique mechanical properties. A tetrachiral honeycomb (TCH) exhibits a bulging effect when subjected to in-plane impact, reducing its Poisson's ratio effect. To improve the performance of TCH, this study proposes two types of axisymmetric tetrachiral honeycombs (ATCH-1 and ATCH-2). First, the in-plane impact performances of TCH, ATCH-1, and ATCH-2 are compared via experiments, and the accuracy of the finite element model is validated. Then, the effects of the different parameters on the deformation modes, energy absorption characteristics, and negative Poisson's ratio effects of the three types of honeycombs are analyzed via finite element models. ATCH-1 and ATCH-2 have higher specific energy absorption (SEA) and a more significant negative Poisson's ratio effect than TCH at an impact velocity of 10 m/s. However, the axisymmetric honeycombs do not have advantages at impact velocities of 50 m/s and 100 m/s. The cylindrical radius r significantly affects the deformation mode of the three types of honeycombs. The axisymmetric design provides a new concept for the novel negative Poisson's ratio honeycomb design. [ABSTRACT FROM AUTHOR]

Aiming at achieving excellent energy absorption capacity, a novel periodic auxetic reentrant honeycomb structure is proposed by defining an octagon honeycomb unit cell with various shape parameters and reentrant angles. Additive manufacturing is applied to fabricate three groups of resin samples with different design parameters. Quasi-static compression experimental test is conducted obtaining the effects of negative Poisson's ratio (NPR) on the compressive stress–strain relationship of the proposed structure. The results show the excellent lateral material shrinkage under axial compression and distinct hardening process with sharp stiffness increase when the structure experiences densification. The experiment results are then used to validate the corresponding 3D finite element models. Good agreements are found between the experiment and finite element simulation results. Furthermore, a geometry parameter study is used to analyze the effect of design parameters on energy absorption capacity of the structure and the results can be a good reference for future optimal design of similar meta -materials. To summarize, in addition to the good energy absorption capacity, thanks to the obvious NPR effects and lateral shrinkage behavior, the newly proposed honeycomb meta-material with specific auxetic reentrant design becomes a solid material with low porosity and high stiffness after full compression to provide further protection or support for its neighbor objectives. [ABSTRACT FROM AUTHOR]