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• The proposed auxetic honeycomb possesses more excellent auxetic behavior and specific energy absorption than the conventional honeycomb. • The interaction between the structural parameters is analyzed. • The multi-objective optimization of the enhanced auxetic honeycomb (EAH) was investigated. • The theoretical model and Box-Behnken Design model were used to predict the mechanical properties of EAH. In response to the challenge of low stiffness and energy absorption capacity, various designs of negative Poisson's ratio (NPR) structures have emerged. However, these designs often lack a comprehensive analysis of other mechanical properties, leading to subpar mechanical performance. Previous studies have explored the mechanical properties response of enhanced re-entrant honeycombs (ERH) under impact conditions, revealing limitations in optimizing the structure's performance with a single objective. Therefore, this study aims to enhance ERH structural parameters to achieve superior mechanical performance through theoretical derivations and geometric optimizations. The results demonstrate that the proposed theoretical model is consistent with finite element analysis and response surface (RS) predictions. Expressions for Young's modulus, specific energy absorption, and compressive strength are proposed, facilitating the identification of structural parameters that meet specific requirements during reverse design. Furthermore, a multi-objective optimization approach optimizes the geometric parameters based on maximum energy absorption and compressive strength. The mechanical behavior of the optimized ERH is investigated using the finite element method, revealing the energy absorption capacity of 13.78 J/g while maintaining Poisson's ratio at -1.06. Additionally, the deformation mode of the optimized structure showcases enhanced stability compared to traditional honeycomb structures. The theoretical model and RS method were used to guide the design of ERH and promote the application of NPR structures. [ABSTRACT FROM AUTHOR]

It has been demonstrated that origami structures can be successfully used for honeycomb structures. And the excellent energy absorption properties of origami structures make them a promising candidate for use in cushioning when paired with honeycomb structures. Consequently, the honeycomb structure was recreated using origami structures to generate new specimens, aiming to reduce the initial peak force under out-of-plane crushing while maintaining the energy absorption properties. The specimens were created using 3D printing technology, and experiments with quasi-static flat pressing were carried out. The properties of the origami-based honeycomb were investigated during out-of-plane crushing, with an emphasis on its energy absorption properties. Additionally, the compressive properties of the origami-based honeycomb are compared with those of traditional re-entrant honeycomb in z-axial directions. To further investigate the properties of the origami-based honeycomb, a validated model was developed in Abaqus, and the accuracy of the finite element model's forecast was confirmed. The results show excellent lateral material shrinkage under axial compression, which is an obvious negative Poisson's ratio (NPR) effect, and a distinct hardening process with stiffness increases when the origami-based honeycomb structure experiences densification. Moreover, compared to the traditional re-entrant honeycomb structure, the origami-based honeycomb has a lower peak crushing force and a smoother plateau stress curve, making it an ideal material for protective structural applications. Increasing the height H or decreasing the forward length V are effective methods for increasing the structure's specific energy absorption (SEA). Additionally, different configurations will have distinct consequences for the structure. Compared to ordinary origami-based honeycombs, the honeycomb with different configurations has superior energy absorption properties and can also achieve stiffness jumps and segmental self-locking. • Under compression, the origami honeycomb displays an evident NPR and densification effect. • This origami honeycomb can effectively utilize the plastic deformation energy of materials. • Differently arranged origami honeycombs suffer stiffness jumps, enabling deformation control. [ABSTRACT FROM AUTHOR]

This article presents the combination of mixed interpolation of tensorial components technique of triangular elements and the edge-based smoothed finite element method (ES-MITC3) developed on the higher-order shear deformation theory (HSDT). The free vibration behavior of auxetic honeycomb sandwich plates with the functionally graded material (FGM) skin layers generated by the proposed program is trained and predicted by an artificial neural network (ANN) model using Matlab coding for reducing computational time and saving computer resources, the proposed approach is expected suitable for practical engineering problems. The strain field of edge-based smoothed triangular elements is approximated by using the generalized C0-HSDT and Lagrange shape functions. Ultra-light features of sandwich plates are obtained by using the auxetic honeycomb core layer (negative Poisson's ratio) and reinforced by FGM skin layers. The present results are compared with other published studies to verify the accuracy and reliability. Besides, the ANN model is also built to train obtained results and accurately predict the natural frequency of structures without running the code. Moreover, the effects of parameters such as geometrical and material properties (especially the auxetic parameters) on the free vibration behavior of auxetic honeycomb sandwich plates with FGM skin layers are investigated in detail. • An edge-smoothed FEM employing the HSDT is developed for vibration analysis of auxetic honeycomb sandwich plates. • The proposed ES-MITC3 element combined with HSDT is more accurate than the original MITC3 element. • Influences of geometrical and material properties on the free vibration of auxetic honeycomb sandwich plates are investigated. • An artificial neural network is established to predict the natural frequency of auxetic honeycomb sandwich plates accurately. • The proposed method can be developed to become the FEM benchmark solutions for auxetic honeycomb sandwich plates. [ABSTRACT FROM AUTHOR]