Closed-form analysis of the thickness effect of regular honeycomb core material

Within a sandwich structure in many cases the effect of a honeycomb core in not only to maintain the distance between the faceskins, but it also contributes to the overall inplane stiffnesses. Due to the coupling of the core displacements with those of the facesheets the stiffness contribution is not simply proportional to its total thickness but a nonlinear function of the core thickness which is the so-called "core thickness effect". In the present work a closed-form description is given for the effective inplane core stiffnesses including the thickness effect. Based on an approximate representation for the displacement field within the core cell walls, the effective core stiffnesses are derived by energetical considerations. The obtained results are validated by accompanying finite element analyses. (C) 1999 Elsevier Science Ltd. All rights reserved.