A bulk material may be reinforced with a stiffer outer layer or a beam structure connected to it. In Abaqus, such layers or beams can be included by creating shells or beams that are tied to the bulk material. It is more efficient, however, to use a skin to model a shell layer, or a stringer to model a beam. With these options additional shell (skin) or beam (stringer) elements are created that share nodes with the underlying mesh. They don’t need to be meshed separately and no tie is required. Properties can be defined similar to regular shell or beam elements.