Effect of inclusions and holes on the stiffness and strength of honeycombs

A finite element study has been performed on the effects of holes and rigid inclusions on the elastic modulus and yield strength of regular honeycombs under biaxial loading. The focus is on honeycombs that have already been w eakened by a small degree of geometrical imperfection, such as a random dis tribution of fractured cell walls, as these imperfect honeycombs resemble c ommercially available metallic foams. Hashin-Shtrikman lower and upper boun ds and self-consistent estimates of elastic moduli are derived to provide r eference solutions to the finite element calculations. It is found that the strength of an imperfect honeycomb is relatively insensitive to the presen ce of holes and inclusions, consistent with recent experimental observation s on commercial aluminium alloy foams. (C) 2000 Elsevier Science Ltd. All r ights reserved.