A novel 3D auxetic meta-structure based on enhanced hexa-missing rib honeycomb

2D auxetic meta-structures face practical limitations, whereas 3D meta-structures offer greater design flexibility, opening up new opportunities to tailor material properties. The 2D enhanced missing rib auxetic honeycombs demonstrate superior mechanical performance, highlighting the need for extending this design to 3D structures. Therefore, based on a previously designed 2D auxetic hexa-missing rib (HMR) honeycomb, a 3D HMR auxetic meta-structure was proposed in the present work incorporating the tension/compression-torsion coupling effect. To deepen the comprehension of potential deformation mechanism and further optimize the design of the structure, a mechanics model of the 3D HMR meta-structure was developed by a simple energy method under small deformation framework. The results indicate that adjusting the geometric parameters allows for achieving targeted mechanical properties over a wide range, enabling them to meet different requirements in engineering applications. In addition, the 3D HMR meta-structure exhibits perfect isotropic behavior and superior auxetic effect compared to the previously proposed 3D tetra-missing rib meta-structure. Finally, the veracity of theoretical formulas was benchmarked by uniaxial experiments and finite element (FE) simulations, where good agreements was observed.