Hexagonal Honeycombs with Zero Poisson's Ratios and Enhanced Stiffness

In view of their potential applications in sandwich structures, there has been increasing interest inhoneycomb networks. Several different types of honeycomb systems have been proposed each exhibitingdifferent mechanical properties. Here we propose a new hexagonal honeycomb structure composed oftwo different geometrical features: a re-entrant feature which is known to generate auxetic behavior,and a non re-entrant feature found in regular hexagonal honeycombs which leads to conventionalbehavior. This results in a ‘‘semi re-entrant honeycomb’’ built of alternate conventional and auxeticlayers. Finite element analysis and analytical modeling of these honeycombs show that they exhibit azero Poisson ratio in one direction and a higher than normal Young’s modulus in the orthogonaldirection. We also show that by virtue of its zero Poisson’s ratio, this honeycomb has a natural tendencyto form cylindrical shaped curvatures, something which is very difficult to achieve with conventional orauxetic honeycombs