Effect of hierarchical features on the critical buckling strength of periodic cellular solids

Periodic cellular solids, due to their ability to provide high stiffness and strength to weight ratios, have become common in engineering applications requiring weight minimization. Such applications relate to aerospace, marine, renewable energy, and automotive industries. The continuously increasing industrial relevance of periodic cellular solids has motivated developing methodologies to improve their elastic and failure properties. Introducing hierarchical features in periodic cellular solids proved as one of the most effective methods to improve their in-plane elastic and strength properties. This approach was applied to aluminum honeycombs and resulted in more than doubling their in-plane stiffness. However, the effect of introducing hierarchical features on the out-of-plane properties of periodic cellular solids in general and honeycombs in particular has not been fully investigated yet. Accordingly, this work investigates the effect of introducing hierarchical features on the out-of-plane behavior of honeycombs. In particular, this work investigates, using finite element computations, the effect of introducing hierarchy on the buckling strength of hexagonal honeycombs. Results show that hierarchy when carefully introduced, can enhance the buckling strength of honeycombs by more than 170% without increasing their weight.