o⇑ MA, Energy absorption

Functionally graded material hin esti last e cr th a s sh a gradual change of the cell wall thickness. Decreasing the relative density in the direction of crushing r fabric d per age as l point impact resistance. The basic applications pertaining to these characteristics are packaging of fragile components (e.g. electronic devices) and various protective products like helmets and shield-ing. Another emerging application is usage of cellular structures as the core material for metal sandwich panels, which are shown to have superior performance over the counterpart solid plates of equal mass under shock loading (Dharmasena et al., 2009; Liang et al., 2007; Mori et al., 2007, 2009; Rathbun et al., 2006; phenomena that include buckling and micro-inertial resistance. The fundamental study of Vaughn et al. (2005) and Vaughn and Hutchinson (2006) has provided much insight into these effects, including the interaction between plastic waves and localized buckling under dynamic loading. Xue and Hutchinson (2006) showed that the micro-inertial resistance of core webs of a square honeycomb metal core increases its resisting force remarkably at early stages of dynamic crushing. At later stages of deformation, the dynamics effects results in suppression of the buckling of the metal webs, leading to emergence of buckling shapes with a wavelength much smaller than the core height. These effects lead ⇑ Corresponding author