Are you talking about composite face sheets bonded to an aluminum honeycomb core? In that case, I recommend shell elements for the face sheets that share topology with solid elements that represent the honeycomb core. You would use orthotropic material properties for the composite laminate and orthotropic material properties for the honeycomb core. This assumes you can obtain the orthotropic material model for the composite laminate.

Copying a paragraph from an earlier post...

One way to make the model solve faster is to replace solid elements on the face sheets with shell elements, however, you will have to do some work to align the material properties to a coordinate system. The reason is solid elements automatically align the material direction to the global coordiantes by default.  However, shell elements automatically align the material direction to the element coordinates by default, and that can result in the material direction randomly pointing in different directions depending on how the face was meshed. You are almost required to override the default direction and define the material direction you want.

If you don't have the orthotropic material properties of the laminate, but you know all the details of the stack of lamina: the material, orientation, thickness and stacking sequence, you can use ACP-Pre to create the material to give the correct properties to the shell element.