I made some benchmark on simply supported composite sandwich panels under uniform pressure using the SHELL SECTION, COMPOSITE.
Considering standard values for carbon skins with G13=G23~4GPa and core shear stiffness G13=G23=20MPa, I could not get similar results to other software (i.e. displacements are lower, error not negligible), whilst applying the same core shear stiffness (or lowest stiffness) to the skins gave me really good results.
I cannot explain why this happens. I guess it is related to the element formulation?