On compressive deformation behavior of hollow-strut cellular materials

We investigated the compressive deformation behavior of hollow-strut cellular materials. The present cellular structure consists of pentagon and/or hexagonal shaped cellular network, where the individual strut cross-section is hollow triangular prism. The porosity of entire cellular material network is 96.5%. Uni-axial compressive test was applied, and both macroscopic (network-level) and microscopic (strut-level) deformation behaviors were investigated. The macroscopic nominal stress-strain curve showed a linear relationship during elastic deformation, and then a stress plateau region was observed, followed by the gradual increase in plastic flow stress. Next, by using X-ray micro-CT technique, the strut geometry was quantitatively identified, and based on which finite element method (FEM) was carried out to elucidate the relationship between the strut geometry and the microscopic/macroscopic elastoplastic deformation. A three dimensional spatial structure unit model was established to mimic the present open-cell structure, where the employed strut material properties were obtained from micro-indentation experiments. The FEM computational result agrees reasonably with experimental one of the macroscopic Young's modulus and yield stress. It also suggests that the stress concentration occurs in the minimum cross-section of strut, and then plastic deformation starts at this local point. Such a local yield phenomenon becomes a trigger of buckling for strut, leading to macroscopic plastic deformation characteristics. Furthermore, strain rate effect of the present cellular material was investigated numerically. The obtained result showed reasonable deformation behavior, but this may be improved in the future. © 2016 Elsevier Ltd.