Design and mechanical properties analysis of a highly anisotropic branch-shaped auxetic structure

Recent studies have revealed that highly anisotropic auxetic structures can be used to design vascular stents. However, current highly anisotropic auxetic structures generally have complex microstructures. Inspired by Y-shaped tree branches in nature, this paper proposed a highly anisotropic branch-shaped auxetic (BSA) structure with a simple and lightweight microstructure. Based on the displacement method, the equivalent analytical formulas for the Poisson's ratio and Young's modulus of this structure were given and verified by experiments and finite element simulations. The results showed that the BSA structure demonstrated high anisotropy, and its Poisson's ratio in the vertical direction reached -20 while retaining a near-zero Poisson's ratio in the horizontal direction. In addition, the half-auxetic mode of the BSA structure was demonstrated, which displayed a near-zero Poisson's ratio during compression and maintained its original auxetic effect under tension. Finally, the BSA tubular structure was investigated, which showed an enhanced volumetric compression ratio and a stable axial length during expansion. This research provides technical support for developing safer and smarter next-generation vascular stents.