SpaceClaim created geometry for a 3D printer to make the wing. This geometry is too complex to mesh. Structural analysis nearly always needs a simplified representation of the true manufactured geometry. In this case, you want to represent the full density 0.8 mm skin as one material property, and the 20% dense core as a second material property.
You can most easily represent the structural model by taking the wing geometry and reduce it by the 0.8 mm skin thickness so you have a solid model of the core. By this I mean the solid has no holes, it is solid with a low density material assigned to it. Mesh that with quadratic tet elements using the core material property. Then use the Surface Coating capability of Mechanical to apply quadratic tri shell elements, with a 0.8 mm thickness assignment, to the surface of the core and use the full density material for those shell elements.