Mixed Mesh (FEM mode)
Use mixed meshing with parts or assemblies that have both solid and thin portions. If you selected mixed meshing, Creo Simulate meshes the solid portion of the model with tetrahedral elements. In addition, it meshes the thin portions of the model with triangular or quadrilateral elements, provided you have defined shell pairs for those areas. Mixed meshing helps avoid the creation of many small tetrahedral elements in thin part features.
Where shell and solid meshed components are in contact along an edge, the software matches up nodes and assigns the default contact type, Bonded. If you want a different contact type, you need to select this before you mesh.
When the mesh generation is complete, shell element nodes align with tetrahedral element nodes at any point on the model where a thin feature attaches to a solid feature.