Hello, I have an assembly of two solid plates bolted together with two bolts. The plates should be composites and the bolts are steel. I was able to insert the assembly into static structural with all parts defined as structural steel but now I want to model the plates as composites and run the static structural like that.

I am having trouble inserting the geometry into ACP (Pre) to model the plates,(see error in image below) does anyone know how I can fix this? Do the plates have to be shells or can they be solids like my model is?