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• A simple re-entrant auxetic metamaterial is designed by rotating and connecting 2D re-entrant honeycomb cells. • The energy absorption of the proposed metamaterial is discussed under different design parameters. • The proposed 3D re-entrant auxetic lattice has desirable stiffness and specific energy absorption. • The initial peak stress and energy absorption capacity of the metamaterial can be adjusted via changing design parameters. As a branch of auxetics, the re-entrant hexagonal honeycomb has many superior mechanical performances. However, most research focused on two-dimensional (2D) re-entrant structures or three-dimensional (3D) structures without high compressibility. The energy absorption capacity of such structures is deficient for practical applications. Therefore, it is important to investigate the 3D re-entrant honeycomb structures which can sustain large deformation in order to make the most use of the materials. In this work, a simple 3D re-entrant unit cell is designed, manufactured and examined. The influence of geometric parameters on the deformation mode and energy absorption capacity is investigated numerically. The experimental results are in good agreement with the finite element prediction. The proposed 3D re-entrant auxetic metamaterial not only possesses a greater bearing capacity but also presents a stable compression deformation. The structure exhibits a desirable energy absorption behavior, including obvious auxetic behavior and a long stress plateau. By adjusting the geometrical parameters of the structure, the performances of energy absorption and compression stiffness can be improved. These findings provide a new idea to design 3D auxetic metamaterials and promote their utilization in protective structures. [Display omitted] [ABSTRACT FROM AUTHOR]

• A novel Diabolo shaped honeycomb based on re-entrant hexagonal honeycomb is proposed. • Four enhanced honeycombs are designed based on the Diabolo shaped honeycomb by adding horizontal or longitudinal ribs. • The simulation results show that Diabolo shaped honeycomb has better impact resistance and energy absorption than re-entrant hexagonal honeycomb. • The plateau stress and specific energy absorption of the honeycomb are significantly influenced by the geometric parameters. This paper presents the design of a novel Diabolo shaped honeycomb (DSH) based on re-entrant hexagonal honeycomb (RHH), and four enhanced honeycombs are designed based on the DSH by adding horizontal or longitudinal ribs. The finite element software ABAQUS/EXPLICIT is applied to investigate the relationship between crashworthiness and energy absorption performance with different impact velocities and geometric parameters. The simulation results show that DSH has better impact resistance and energy absorption than RHH. DSH has improved plateau stress by 141.3%, 78.7%, and 22.7% of low-velocity, medium-velocity, and high-velocity compression, respectively, and SEA by 103.7%, 79.3%, and 7.3%, respectively. In addition, the impact resistance of the four enhanced honeycombs is further improved. The shrinkage effect of DSH after impact is not as good as that of RHH, and the horizontal ribs suppress the negative Poisson's ratio property of the honeycomb. Different impact velocities affect the deformation pattern of the honeycomb. With the increase of impact velocities, the honeycomb has a transition from overall deformation to local deformation with increasing velocity. The plateau stress and specific energy absorption of the honeycomb are significantly influenced by the geometric parameters. This research provides a reference for the optimal design and application of honeycombs as energy absorbing components. [Display omitted] [ABSTRACT FROM AUTHOR]