The Layered Linear Elastic Material node adds the equations for a layered linear elastic membrane.

If the Composite Materials Module analysis is available, this material model can be applied to arbitrary layers in a multilayered membrane. The material properties, orientations, and layer thicknesses are defined using Layered Material node. The offset, and local coordinate system, in which material orientations and results are interpreted, is defined by Layered Material Link or Layered Material Stack node.

Without the Composite Materials Module, only single layer membranes can be modeled. This is still useful, for example for some multiphysics couplings. For single layer materials, an ordinary Material node can be used, as long you include a Shell property group in which, for example, the thickness is given.

By adding the following subnodes to the Layered Linear Elastic Material node you can incorporate many other effects:

Some of these material models are only available together with the Nonlinear Structural Materials Module (see http://www.comsol.com/products/specifications/).

For this node, the Shell Properties section is only used for selecting a material model, but not individual layers.

The boundary selection in this node is similar to the Linear Elastic Material node. It is however only possible to select boundaries which are part of the selection of a layered material defined in Layered Material Link or Layered Material Stack node.

Select a linear elastic Solid model — Isotropic, Orthotropic, or Anisotropic and enter the settings as described for the Linear Elastic Material for the Solid Mechanics interface. If the layers have different types of anisotropy properties, select the one that is most complex.

For a material with a very low compressibility, using only displacements as degrees of freedom may lead to a numerically ill-posed problem. You can then use a mixed formulation, which add an extra dependent variable for either the pressure or for the volumetric strain, see the Mixed Formulation section in the Structural Mechanics Theory chapter.

From the Use mixed formulation list, select None, Pressure formulation, or Strain formulation.

In this section there is one check box Force linear strains. If a study step is geometrically nonlinear, the default behavior is to use a large strain formulation in all domains. There are however some cases when you would still want to use a small strain formulation for a certain domain. In those cases, select the Force linear strains check box. When selected, a small strain formulation is always used, independently of the setting in the study step.

When a geometrically nonlinear formulation is used, the elastic deformations used for computing the stresses can be obtained in two different ways if inelastic deformations are present: additive decomposition and multiplicative decomposition. The default is to use multiplicative decomposition. Select Additive strain decomposition to change to an assumption of additivity.

Select the Calculate dissipated energy check box as needed to compute the energy dissipated by Creep, Plasticity, Viscoplasticity or Viscoelasticity.

Physics tab with Membrane selected: