Compression behavior of novel asymmetric negative Poisson's ratio sandwich structures: theoretical, experimental, and numerical analysis

Five types of re-entrant honeycomb sandwich structures—a symmetrical re-entrant honeycomb (SRH), an outward-expanding asymmetric re-entrant honeycomb (OARH), an inward-contracting asymmetric re-entrant honeycomb (IARH), and hybrid structures of OARH and IARH (HOARH and HIARH, respectively)—are developed using the 3D printing technology. A theoretical model is established to predict the plateau stress of asymmetric re-entrant honeycomb sandwich structures. The quasi-static compression behaviors of the sandwich structures under varying pressure plate conditions are investigated using experimental, finite element, and theoretical methods. Results indicate that the theoretical predictions and simulations agree well with the experimental findings. The asymmetric design enhances the mechanical performance of the sandwich structures. While the outward-expansion design enhances the mechanical properties and negative Poisson's ratio effect, the inward-contraction and hybrid asymmetric designs enhance the structural stability. The SRH, OARH, and HOARH sandwich structures experienced sliding and accelerated failure on the weaker side under inclined loading conditions, reducing their energy-absorption capacity, whereas the more stable IARH and HIARH sandwich structures were less affected. The OARH sandwich structure, with a lightweight design, exhibited the best performance under different loading conditions and improvements of 17.59 %, 89.93 %, and 23.38 % in the plateau stress, specific stiffness, and specific energy absorption, respectively, compared with the SRH sandwich structure. Parameter analyses indicate that increasing the wall thickness enhanced the load-bearing and energy absorption capacities of the OARH sandwich structure; however, the difference between its two angles should not exceed 15°. This study provides valuable guidance for the design and application of re-entrant honeycomb sandwich structures.