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composite core ramps and adhesive layers

Hello, all. I've read these forums for several years, but this is my first time posting anything.

 

Briefly, I am trying to improve the resolution/accuracy of a model. The model is of a automobile composite panel with a fairly elaborate core profile (several different ramped segments, intersecting at various angles). The original model used laminate plates, which we just staggered in defined thickness to capture the ramped/sloped areas.

 

But we're trying to do better than that, and I now have a model with 3D solid mesh for the core (with appropriate anisotropic properties) and laminate plate elements on either face for the various laminates on the faces of the sandwich. I have bonded the plate elements to the core (and in a few locations, due to some design peculiarities, to each other) with glue contacts. The whole thing works well as far as running the solution goes, but I'm not convinced I can predict delamination or adhesive failures with this approach.

 

Can anyone give me any insight onto what vectors I should be pulling/manipulating to really understand my ply failure modes when using an approach like this? Or is this approach misguided? I can still go back to something more like the 2D approach, though the ramp had so many different thicknesses, the model became very elaborate and hard to edit/maintain. And we'd still have the question of whether we're capturing ramp zone stresses correctly.

 

If there are any relevant discussions or tutorials in the standard documentation, please let me know. I'm running Femap 11.3.1 with the NX Nastran solver.