The Linear Elastic Material, Layered 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 Linear Elastic Material, Layered 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 Single Layer Material, 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, Strain formulation, or Implicit 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.

Select a Formulation — From study step (default), Total Lagrangian, or Geometrically linear to set the kinematics of the deformation and the definition of strain. When From study step is selected, the study step controls the kinematics and the strain definition.

To have full control of the formulation, select either Total Lagrangian, or Geometrically linear. When Total Lagrangian is selected, the physics will force the Include geometric nonlinearity check box in all study steps.

Select a Strain decomposition — Automatic (default), Additive, or Multiplicative to decide how the inelastic deformations are treated. This option is not available when the formulation is set to Geometrically linear.

The Strain decomposition input is only visible for material models that support both additive and multiplicative decomposition of deformation gradients.

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: