How to model a composite helicopter blade cross section?

Hi friends,

I am working with abaqus in GUI for two years for modeling heat transfer analysis and I am switched to structural mechanics now. I need to model a closed central cross section (like helicopter blade) which has offset composite layers wrapped over it (2-3 times). Can anybody tell me how to model it? I tried shell planar but in this way the adding up layers might be ok, but there is hollow inside the center which I need to make solid. I created a 2-d cross section and extruded it and then pade partions as layers throughout the length, but it failed after running saying: 240 elements have missing property definitions. I want to make the cross section as: steel or aluminum at the center core, top layer as composite, next top layer as another composite like this. I tried lots of times but could not do it. There is no such video also in youtube. Can anybody help?