Influence of cell wall curvature radius and adhesive layer on the effective elastic out-of-plane properties of hexagonal honeycombs

Abstract

Numerical modeling of honeycomb structures in aerospace engineering is too tedious and time consuming. The homogenization of these structures permits to obtain an equivalent orthotropic homogeneous solid and its elastic effective properties and thus realizing very efficient simulations. In a sandwich structure the most important effective constants of the core are the out-of-plane shear moduli G23 and G13. These particular effective constants can be obtained analytically, numerically or, if available, can be taken from the producer's data sheets. In the last case they are generally obtained experimentally, but only for some particular thicknesses of the cores and sandwich faces. The analytical models usually neglect the curvature radius of the cell walls and the adhesive layer influence by using some additional hypotheses. In this paper a general parameterization of commercial honeycombs is first discussed. Then, neglecting the skin effect and considering the rigid skin effect, the out-of-plane properties of the core are obtained using a finite element analysis of a representative volume element. The numerical results are analyzed by comparing them to the ones given by the existing analytical models and/or experimental data and their advantages and pitfalls are discussed and explained. The results provide new insights into understanding the mechanics of honeycombs.

Keywords

• hexagonal honeycombs
• node bond adhesive
• Finite Element Analysis
• effective elastic properties
• adhesive thickness and fillet