Hello everyone:

I want to get the frequency of a sandwich panel, it has 2surfaces and a honeycomb core. When I use the conventional shell model, the result is ok, compared to the experiment, no problem. But When I used continuum shell model, it goes bad. The first frequency is wrong, and its vibration shape is quite wrong, its 2 surfaces are crossed. The material is the same, so what is the reason of this problem? Thanks to everyone.

The left picture is the continuum shell vibration shape, the right is conventional shell.