Testing and modeling tearing and air effect of aluminum honeycomb under out-of-plane impact loading

For the deformable barrier often used in full-car crash tests, which mainly consists of aluminum honeycombs, tearing in the thin-walled structure of honeycomb is a common phenomenon induced by non-uniform large deformation, and influence of the entrapped air proves non-negligible when the honeycomb undertakes dynamic loading. Both the localized tearing and the entrapped air affect the deformation pattern and the global mechanical response of the honeycomb in crash scenarios. The present paper documents development of an equivalent finite element model (FEM) for the aluminum honeycomb focusing on these two effects as well as the relevant experimental study. Four tests of the honeycomb block with out-of-plane loading, i.e., uniform compression, compression-shear along two orthogonal cross-sections and indentation, are performed at quasi-static and dynamic loading speeds to quantitatively address the tearing effect and the air effect on the entire mechanical response. It is also found that the honeycomb exhibits different tearing mechanisms along the two orthogonal cross-sections. In developing the solid-element based equivalent model for the honeycomb, airbags are introduced to characterize the air effect, and beam elements with failure criteria are embedded to simulate the tearing effect: Parameters of the airbags and the beam elements in the equivalent FEM are determined based on different combinations of the honeycomb tests. Simulations of all the loading cases in the present study achieve good agreement with the test results in terms of the global mechanical response and overall deformation pattern, reflecting feasibility of the equivalent FEM.