Reply To: Honeycomb structure, adhesive contact

[peteroznewman]

Yes, there is a simple way to model honeycomb sandwich panels in ANSYS. Honeycomb behaves as an orthotropic material, which means the properties change with the direction through the material. You can create an orthotropic material model in ANSYS for the honeycomb core that looks like this.

Note that honeycomb core is stiffer in shear in the L direction than the W direction, so you have to use a coordinate system in ANSYS to orient the material the way you want to for your application.

The material for the aluminum face sheets would be like the aluminum that is included in the materials database, which is an isotropic elastic material.

In CAD, you create a solid body with the thickness of the honeycomb core and the outline of the shape of the panel you are using. The top and bottom face sheets that bond to the honeycomb core can be created as either solid bodies or as sheet bodies. This is a very lightweight representation of the honeycomb sandwich since you don't model the individual cells. Those are represented by the material property assigned to the solid body that encloses the volume of the honeycomb core.

If you create the face sheets as solid bodies, you will have three bodies for the sandwich structure. In DesignModeler, select those three parts and Form New Part to create a single part with three bodies. When you mesh in Mechanical, common nodes at the coincident surfaces will hold each face sheet to each side of the core thickness. These three bodies should be sweepable so you will have an efficient hex mesh to represent the sandwich (not a tet mesh). Make sure you have two or more elements through the thickness of each solid body.

Well made aluminum honeycomb sandwich should fail in the core itself, and not by the epoxy failing. Therefore you don't need to include the epoxy in the model as it is stronger than the aluminum honeycomb core. Vendors of honeycomb core publish the strength of the core. The table below shows the values of shear strength that can be compared with the shear stress computed in the ANSYS model to determine if a failure is predicted for that load. 

Note that if you have a much lower stress than the strength shown above, but the stress cycles between zero and positive stress or negative and positive stress values, the core can exhibit a fatigue failure. Unfortunately, manufacturers rarely publish fatigue strength values or S-N fatigue curves, so you would have to do your own fatigue testing if cyclic loading is expected.