The underlying principle of ACP is that a composite lay-up is defined on a shell geometry. The model of the lay-up that is passed from the ACP preprocessor to the solver can be a shell element mesh but also a solid or a solid shell element mesh. The solid model mesh is an extrusion of the shell element input mesh. If this input shell mesh uses linear elements (SHELL181) the solid model mesh generated in ACP can have either layered solid elements (SOLID185) or layered solid shell elements (SOLSH190). If it is quadratic (SHELL281) the solid model mesh can only have quadratic layered solid elements (SOLID186).

The geometry and loading of the engineering problem ultimately dictate what element type is best suited for the analysis. The following sections outline a few general considerations about the element types in ACP. For more detailed information, see Element Library in the Mechanical APDL Theory Reference.