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Novel honeycombs with buckling-induced features and tailorable properties have been designed and fabricated using the fused deposition modeling (FDM) method. Quasi-static out-of-plane compression tests were carried out to investigate the topological dependence of the crushing behavior of the buckling-induced honeycombs (BIHs). The results demonstrated that the crushing performance of BIHs can be artificially controlled by altering their shape parameters. In particular, the initial peak force (IPF) and the undulation of the mechanical response of BIH can be effectively reduced by increasing the layer number or arranging the asymmetric layers. A finite element model validated against experimental results was also utilized to reveal the underlying deformation mechanism and study the corresponding displacement-crushing force responses for BIHs with different topological parameters. It was uncovered that the buckling-induced mechanism is beneficial for tuning the stiffness and mitigating local buckling resistance through the pre-determined collapse behavior of cell walls. Further, a multi-objective optimization process of BIH was performed to seek the optimal design solution for energy-absorbing structures in specific scenarios. The findings of this study provide a theoretical basis for the development of new ideas and optimization solutions for the design of lightweight and performance-tailored energy-absorbing structures. [ABSTRACT FROM AUTHOR]

Flexible hexagonal honeycomb cores exhibit nonlinear elastic properties due to the large geometric deformation. To rapidly and efficiently analyze the mechanical properties of honeycomb sandwich structures, it is standard to replace the actual core structure in analyses with a homogenized core material presenting reasonably equivalent elastic properties. As such, a convenient and efficient method is required to evaluate the equivalent elastic properties of flexible hexagonal honeycomb cores. The present work develops analytical expressions based on a deformable cantilever beam under large deformation. On that basis, the equivalence expressions are improved by including the stretching deformations of the honeycomb structure on an infinitesimal section of a unit cell. Finite element analysis and experimental testing are subsequently performed for two examples of flexible hexagonal aluminium and Nomex ® honeycomb cores. Both computational and experimental results indicate that their equivalent elastic moduli have the different variation with high strain in the two characteristic orthogonal directions. The analytical predictions demonstrated that the improved analytical expressions are more suitable to flexible honeycomb cores under conditions of high strain and low elastic modulus. It is further revealed that the structure of Nomex honeycomb cores result in different forms of damage during failure along the different load directions, which lead to differing equivalent properties in the orthogonal directions when the strain limit is reached. [ABSTRACT FROM AUTHOR]

Auxetic cellular structures with outstanding mechanical performance and unique deformation characteristics have a variety of potential applications in aerospace, as ultralight load-bearing structures and vibration isolation structures. Herein, the in-plane compression behaviors of hybrid honeycomb metastructures, comprised of conventional and auxetic honeycombs, are systematically studied by using theoretical calculations, experimental characterization and numerical simulations. The theoretical formulae of elastic modulus and ultimate strength of the architected metastructure are derived by establishing stress analysis models. Three types of hybrid honeycomb metastructures are manufactured by selective laser melting (SLM) with 304 stainless steel. Finite element analysis is performed to unveil the deformation mechanism and failure modes. The theoretical prediction results of elastic modulus and ultimate strength are consistent with simulations and experimental results. In addition, the influences of panel and layer numbers on the mechanical behavior of hybrid honeycomb metastructures are discussed in detail. The results reveal that a hybrid metallic honeycomb metastructure, with stable and superior compressive properties, can be obtained by combining two types of cellular cells, i.e., conventional and auxetic honeycombs. These results provide a baseline for further research and development of novel metastructure designs. [ABSTRACT FROM AUTHOR]