Undulation of the honeycombs׳ plateau stress under impact and the dynamic enhancement—Theoretical analysis

The analytical expression of the detailed undulation of the plateau stress of the hexagonal honeycombs under the low-velocity and the middle-velocity crushing is deduced, which consists of the static term and the dynamic term. It is shown that the level of the honeycomb׳s stress significantly decreases with the increase of the cell-wall angle under both the low-velocity and the middle-velocity impacts, which is mainly attributed by the static term in the expression of the honeycomb׳s stress. The inertia effect of the cell structures results in not only the higher level of the stress with the impact velocity but also the different shape of the honeycomb׳s stress curves between the low-velocity and the middle-velocity impacts. A dynamic sensitivity index is used to quantitatively evaluate the sensitivity of the honeycombs׳ plateau stress to the impact velocity. It is revealed that the dynamic sensitivity of the honeycombs is inversely proportional to the honeycomb׳s relative density, while it becomes stronger with the increase of the cell-wall angle β, which enlightens the methods to reduce or strengthen this sensitivity of honeycombs according to the industry requirement in applications.