Multi-Level Modeling of Low Velocity, Low Energy Impact on Metal-Skinned Sandwich Structure

The research objective is to model the low velocity/low energy impact on sandwich structures with metallic skins. A progressive approach is carried out by considering first the honeycomb core alone, then static indentation on sandwich structures and finally a dynamic analysis. During the first step, a phenomenological study of the behavior of honeycomb subjected to crushing is completed. It appears that local rotations and cell edges plays an important role in the crushing phenomenon. It is then possible to propose a simple analytical model able to represent the indentation of honeycomb alone for various indenter geometries by modelling only the cell edges behavior. The compression law of the cell edges is identified by a basic uniform compression test. This key-idea is then used to create a finite element model using a grid of nonlinear springs to represent the honeycomb structure. The contact law of static indentation tests of metal-skins Nomex™ honeycomb sandwich structures can thus be found numerically and agree well with the experiments. Finally, this contact law can be used to model dynamic impacts which demonstrates the static/dynamic equivalence for this range of impact and structures.