On stiffness properties of square honeycombs and other unidirectional composites

In this paper we consider stiffness properties of square symmetric unidirec tional two-phase composites with given volume fractions. First, we compare the effective moduli of the stiffest possible (or softest possible) of such materials which satisfy transverse isotropy or square isotropy with that o f materials satisfying 3D-isotropy. Next, we present some numerical FEM computations of in-plane stiffness prop erties of square honeycombs. Our results are compared with the effective mo duli of the stiffest possible square symmetric composites. The numerical re sults are used to optimize the directions of square prisms in the core of s andwich plates with respect to stiffness. Our calculations can therefore be useful in connection with optimization of structural topology. (C) 2001 Pu blished by Elsevier Science Ltd.