The Membrane interface includes several material models; Linear Elastic Material, Linear Elastic Material, Layered, Nonlinear Elastic Material, Hyperelastic Material, and External Stress–Strain Relation.

The fundamental difference between Linear Elastic Material and Linear Elastic Material, Layered is that in Linear Elastic Material the material properties are assumed to be constant through the thickness. In the Linear Elastic Material, Layered model, there is a numerical integration in the thickness direction, and it is also possible to store states, such as inelastic strains, at different through-thickness locations.

When the Composite Materials Module is available, the Linear Elastic Material, Layered model can be used to model multilayered membrane. This is the main use of this material model. It is, however, also used for the Thermal Expansion, Layered multiphysics coupling, even if there is just a single layer.

For each layer, you have the option to set the resolution in the thickness direction. In a layered material, this is the Mesh elements property in the layer definitions. When working with a single layer material, then it is the Mesh elements property in the Shell property group. For membrane analysis, you can set this value to ‘1’ since in-layer variations are not part of the theory.