Evaluations of three-point bending and energy absorption performances of novel auxetic honeycomb circular tubes under different impact loading

Tubular structures are extensively applied in engineering, with emphasis on reducing structural weight while improving mechanical properties. Auxetic honeycomb structures, recognized for their excellent mechanical performance and high design flexibility, present a promising alternative. Therefore, this present study aims to design a gradient auxetic circular tube (ACT) by adjusting the number of radial honeycomb layers. The structure's bending performance, deformation patterns, and energy absorption capabilities are evaluated through three-point bending tests and finite element simulations. The influences of auxetic effect, number of honeycomb cells, cell wall thickness, re-entrant angle, loading position and speed on the bending performance are systematically evaluated. The results demonstrate that the ACT structure exhibits greater energy absorption and load-bearing performance than the non-auxetic circular tube. Specifically, there is an enhancement in specific energy absorption (SEA) by 6.2 %. For given inner and outer diameters, the energy absorption performance increases with the layer count of the auxetic honeycomb. The addition of cells to the ACT structure can enhance its auxetic effect and bending performance. A thicker cell wall can effectively boost both energy absorption performance and load-bearing capacity. The bending resistance is improved with an increase in the re-entrant angle. The effects of different loading positions on the structure are examined, and the optimal loading position is identified. As the loading speed increases, the ACT structure shows higher plateau force and better energy absorption performance. The research results present a new design approach for achieving lightweight tubular structures with high specific strength and energy absorption performance.