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The natural beesʼ honeycombs maintain long-term structural stability in harsh environments, employing a highly material-efficient approach. However, the reasons remain somewhat ambiguous. To clarify the stabilization mechanism and investigate quasi-static compression responses of double-layer ordered cellular structures, honeycomb, Tóth and single-layer cellular structures with a relative density (ρ r) of 25.84 % were fabricated using 3D printing technology. Then, quasi-static compression experiments in three directions were conducted. Further, a numerical study was conducted to uncover the stabilization mechanism and effect of ρ r on compressive behaviors. Results revealed that the stabilization mechanism was mainly attributed to bearing load priority of intermediate layer and its inhibition on formation of plastic hinges. A relative density of 5.17 % served as a transition point for deformation mode, beyond which honeycomb and Tóth structures exhibited stronger in-plane compressive strength at expense of less sacrificed out-of-plane compressive strength, below which they both exhibited more stable compressive curves compared to single-layer cellular structures, which were favorable for energy absorption. This study clarifies the stability mechanism of beesʼ honeycombs and addresses the lack on compression behaviors of double-layer ordered cellular structures. Moreover, it introduces two available bionic structures with controllable deformation modes to expand the application of single-layer cellular structures. [ABSTRACT FROM AUTHOR]

Honeycomb structures exhibit outstanding mechanical properties with specific unit cell configurations. We introduce a novel honeycomb structure that can enhance the compression property and energy absorption capacity by utilizing four-dimensional (4D) printing technology with polylactic acid (PLA) materials. In the designed honeycomb structure, the walls of the adjacent unit cells are independent, and the shape of the unit cells can be transformed between a hexagon and triangle under external loading and temperature stimulus. 4D printing technology is employed to prepare the honeycomb specimens, and the deformation processes of the innovative honeycombs are implemented. Structure I (a novel hexagonal honeycomb structure) and Structure II (a semi-triangular honeycomb structure) can be transformed into each other. Uniaxial quasi-static compression and impact tests are conducted to investigate the compression property and energy absorption capacity of the designed honeycomb structures. The results indicate that the novel honeycomb had a high compression property with Structure II, and had high energy absorption capacity with Structure I; thus, the developed honeycomb structures have broad application prospects for the multifunctional applications of honeycomb structures in the future. [ABSTRACT FROM AUTHOR]

[Display omitted] • Spinal interbody cages adapted for an auxetic, and honeycomb using standard CAD software operations and manufactured with SLM. • Auxetic-based cages exhibit higher strength properties than honeycomb-based cages. • The stiffness of the auxetic cages is comparable to stiffness of human cortical bone. • The honeycomb cages exhibit lower value of Young's modulus closer to that for vertebrae. This paper presents a method for modeling a biomedical device by adaptation a commercially available interbody cage for an auxetic metamaterial and honeycomb structure using standard operations in Computer-Aided design software. The mechanical properties of experimental prototypes of Ti-6Al-4 V cages made by selective laser melting using computer modeling (finite element analysis), static and low-cycle fatigue compression tests (up to 3500 cycles) are characterized. 3D printed cells with structures with an angle of inclination between cell edges of less than 90˚ (auxetic metamaterial) are shown to exhibit higher static compressive strength and fatigue resistance than cells based on structures with an angle of inclination greater than 90˚ (honeycomb structure). The changes in the inclination angle differently affect to the porosity and consequently to mechanical behavior of auxetic metamaterial and honeycomb structure. The Young modulus of the auxetic-based interbody cage is 6.68 ± 0.28 GPa and comparable to the elastic modulus of human cortical bone. The honeycomb-based cage exhibits lower values of Young modulus (1.19 ± 0.03 GPa) close to that of trabecular bone and vertebrae. Importantly, the auxetic-based cage is not destroyed after 3500 cycles under 14 kN load with residual deformations ≤ 1 % (0.21 ± 0.10 mm displacements). [ABSTRACT FROM AUTHOR]