Size effect of composite Kagome honeycomb sandwich structure reinforced with PMI foams under quasi-static bending: Experiment tests and numerical analysis

摘要

Polymethacrylimide (PMI) foams reinforced composite Kagome honeycomb sandwich structures (PKCSSs) are a new class of structure with great application potential in aerospace and navy. They have the advantages of convenient processing, low production cost, and high modulus and strength with light weight. In this paper, five PKCSS specimens with different sizes were fabricated and the size effect was studied through three-point bending (TPB) tests. By analyzing unit cell structures, theoretical models were established for PKCSS equivalent bending stiffness and core density. Combining bending failure theory of sandwich structures, PKCSS bending failure equation was derived. It was witnessed that experimental results were highly consistent with those obtained from the theoretical model. Relationships among equivalent modulus, core density, rib width, node spacing, and rib angle were also studied. Factors affecting the ultimate bending strength of PKCSS were analyzed and critical strength surface and corresponding failure mode maps were determined. This study revealed the effect of structural size on the bending characteristics of PKCSS, discussed the change rule of PKCSS bending strength and stiffness, and determined the optimal size design ratio and design suggestions.