Mechanical properties and multi-objective optimization of reinforced re-entrant honeycomb sandwich structures under bending load

The catenary reinforced method can enhance the crashworthiness of re-entrant honeycomb (RH) by avoiding hollow structural characteristics, strengthening negative Poission’s ratio effect, and utilizing the high load-bearing effectiveness of catenary structures. Based on the above effects the sandwich beam with reinforced RH (RRH) was proposed. The metallic specimens from the proposed structure were fabricated for three-point bending tests. Results show that the introduced catenary structure can limit the rotation deformation of inclined cell walls around vertices, and the drop in load-bearing force after initial plastic deformation is reduced from 29.3% to 6.6%. Compared to classical RH cored beams, the maximum load-bearing force and energy absorption of RRH ones can be improved by 26.7% and 8.9%, respectively. A parametric analysis was conducted to reveal that the thicknesses of front facesheet, back facesheet, and core had a significant effect on deformation behavior and energy absorption of RRH cored sandwich beams. The thickness of front facesheets, cores, and back facesheets was employed as optimization variables, and the mass, maximum load-bearing force, and energy absorption were used as optimization objectives to perform the multi-objective optimization of RRH cored sandwich beams. The optimized sandwich beam exhibits increases of 64.9% in maximum load-bearing capacity and 46.9% in energy absorption. The impact resistance of conventional honeycomb sandwich beams under in-plane and out-of-plane loading was compared at identical wall thickness and mass, respectively. Analysis demonstrated the superior energy-absorbing protective performance of the proposed RRH sandwich beams. The research results can provide useful guidance for the reinforcement design of honeycomb cored sandwich beams.