Bending response and energy absorption of sandwich beams with novel auxetic honeycomb core

In recent years, the enhanced auxetic honeycomb structure has attracted attention owing to its high strength and negative Poisson's effect. The purpose of this study is to explore the bending response and energy absorption of the star-triangular honeycomb core (STH-C) and sandwich beam with an STH-C (STH-SW). Three-point bending tests and a series of numerical simulations are conducted to investigate the bending performance of the sandwich beams. The results indicate that STH-C exhibits only local bending deformation in the loading region, whereas the cells of the STH-SW undergo shrinkage deformation in the loading region, and the neighboring cells undergo tensile deformation. In addition, the deformation mode of the STH-SW is influenced by the compression position and structural parameters. Increasing the face sheet thickness and changing the thickness arrangements is beneficial to improving the load-bearing capacity of the sandwich beams, especially when tf/tb > 1. Furthermore, the load-bearing capacity of the sandwich beams increase with the increase of the cell-wall angle and t/l, and increasing the t/l can change the cells from a global deformation to a local deformation mode. Subsequently, the complex proportional assessment method (COPRAS) is implemented to determine the influence weights of the structural parameters on the load-bearing capacity of the sandwich beams. The results demonstrate that the cell structure parameters have a more significant influence on the bending performance, especially the t/l. Finally, the bending performance of the STH-SW is compared with that of sandwich beams with different cores (star-shaped, re-entrant hexagonal and triangular corrugated structures). The results show that the energy absorption capacity of the STH-SW is 24.34% and 37.97% higher than that of sandwich beams with star-shaped and re-entrant hexagonal cores, respectively. Although the energy absorption capacity of the STH-SW is 10.25% less than that of multi-layer triangular corrugated core sandwich beam, there is no initial peak load for the STH-SW. This study is expected to provide some insights for further investigations on the bending performance optimization of sandwich beams with auxetic cores.