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

If the Composite Materials Module analysis is available, this material model can be applied to arbitrary layers in a multilayered shell. 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 shells can be modeled. This is still useful. In particular, it is used for nonlinear material models, but also 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 https://www.comsol.com/products/specifications/).

For this node, the Shell Properties section is mainly used for selecting a material model, but not individual layers. There is one exception: it is possible to select a single stack member. This is useful when combining the Shell interface and the Layered Shell interface on the same boundary (sometimes called the multiple model method)

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 a Layered Material Link or a Layered Material Stack node.

Select Material symmetry— 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 adds 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.

To display this section, click the Show More Options button () and select Advanced Physics Options in the Show More Options dialog box.

If the Solve for out-of-plane strain components check box is selected, extra degrees of freedom will be added for computing the out-of-plane strain components. This formulation is similar to what is used for plane stress in the Solid Mechanics and Membrane interfaces, and it is computationally somewhat more expensive than the standard formulation. See Plane Stress.

In the default formulation, the out-of-plane strain in the shell is explicitly computed from the stress, and no extra degree of freedom is added. This may cause circular references of variables if you for example want the constitutive law to be strain dependent. If you encounter such problems, select the Solve for out-of-plane strain components check box.

When the Mixed Formulation is used, the Solve for out-of-plane strain components check box is selected, the extra degrees of freedom are added, and the section Out-of-Plane Strain is hidden.

In this section there is a list for defining the value of shear correction factors. The two options available are Automatic and User defined. Once User defined option is selected, you can enter the values of k23 and k13.

If a study step is geometrically nonlinear, the default behavior is to use a large strain formulation in all domains. Select the Geometrically linear formulation check box to always use a small strain formulation, irrespective 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.

If Pressure formulation is used, select the discretization for the Auxiliary pressure — Automatic, Discontinuous Lagrange, Continuous, Linear, or Constant. If Strain formulation is used, select the discretization for the Auxiliary volumetric strain — Automatic, Discontinuous Lagrange, Continuous, Linear, or Constant.

Physics tab with Shell selected: