Honeycomb

Abstract: Lightweight metallic cellular materials can be used in the construction of composite plates, shells and tubes with high structural efficiency Previous models for the mechanical performance of cellular materials have focused on their dependence on relative density, cell geometry and the properties of the solid material of which the cell faces and edges are composed In this study, we consider the effect of the distribution of solid between the cell faces and edges on mechanical properties using finite element analysis of idealized 2D (hexagonal honeycomb) and 3D (closed-cell tetrakaidecahedral foam) cellular materials The effects of the distribution of the solid on the stiffness and strength of these materials are presented and discussed

Abstract: In the mechanical testing of metallic foams, an important issue is the effect of the specimen size, relative to the cell size, on the measured properties. Here we analyze size effects for the modulus and strength of regular, hexagonal honeycombs under uniaxial and shear loadings. Size effects for indentation of a honeycomb are evaluated using finite element analysis. Finally, the results for honeycombs are extrapolated to foams. The results are compared with data for metallic foams in the following, companion paper.

Abstract: The effect of low density filler material, such as aluminum honeycomb or foam, on the axial crushing resistance of a square box column under quasi-static loading conditions is studied. Numerical simulation shows that in terms of achieving maximum energy absorption, filling the box column with aluminum honeycomb can be preferable to thickening the column wall. Superior specific energy absorption is also obtained by filling the column with moderate or high strength aluminum foam. Simple formulas for the relationship between mean crushing force and the strength of filler are developed. Moreover, the presence of adhesive increases energy absorption significantly compared to unbonded filling.

Abstract: The in-plane mechanical behavior of honeycombs has been widely used as a two-dimensional model of the behavior of more complicated space filling foams. This paper deals with the mechanisms governing in-plane crushing of hexagonal aluminum honeycombs. Finite size honeycomb specimens are crushed quasi-statically between parallel rigid surfaces. The force–displacement response is initially stiff and elastic but this is terminated by a limit load instability. Localized crushing involving narrow zones of cells is initiated and subsequently crushing spreads through the material while the load remains relatively constant. When the whole specimen is crushed the response stiffens again. It has been found that although the crushing patterns that develop during the load plateau vary from specimen to specimen (influenced by geometric imperfections and by specimen size) the underlying cell collapse mechanism is common to all specimens. As a result, the level of the stress plateau and its extent in strain are quite repeatable. The crushing process is simulated numerically by full-scale FE models in which the geometric characteristics of the actual cells are used. The manufacturing of the honeycomb involves cold expansion of specially bonded aluminum sheets. This is simulated numerically in order to reproduce the material changes and residual stresses introduced to the aluminum by the process. The expanded honeycomb is then crushed as in the experiments. It is demonstrated that once the key geometric, material and processing parameters are incorporated in the models, the simulations reproduce the experimental results both qualitatively as well as quantitatively.

Abstract: The bare aluminum alloy (A5052) honeycomb is compressed in the longitudinal direction of the cell. Effect of the cell shape and the foil thickness on crush behavior is investigated by the numerical simulation using an explicit FEM code DYNA3D. Impact experiment using a drop-hammer apparatus whose impact velocity is 10 m/s and the corresponding quasi-static one are also performed. In the impact experiment, compressive stress increases with the hammer travel due to the air enclosed in the honeycomb cells. However, the nominal stress at the incipient compression is very similar for both the cases. In computation, numerical model of one ‘Y’ cross-sectional column is used and the impact velocity is 10 m/s. Internal angle of branch in ‘Y’ cross-section ranges from 30° to 180°. The numerical result shows that the cyclic buckling mode takes place in every case and that the crush strength is higher for smaller branch angle. It increases with the foil thickness. However, when the crush strength is evaluated with respect to the net cross-section of the material part only, it attains the maximum value when the cell shape is of regular hexagon. Numerical results are well consistent with the corresponding experimental ones.