Add a Boundary to Boundary node to connect two shell boundaries that are geometrically disjoint. It is assumed that the boundaries are parallel. The connection between corresponding points on the two edges can be rigid or flexible.

Select the coordinate system to use for specifying the stiffness in the case of a flexible connection. From the Coordinate system list select from:

Select a Method — Rigid or Flexible.

For Rigid, the coupling between the two boundaries is rigid in a pointwise manner. Every node on the destination boundary is coupled by a virtual rigid bar to the nearest point on the source boundary. This does not imply that the whole boundary is rigid. Such a coupling can be obtained using a Rigid Connector.

For Flexible, select Connection properties — User defined or From material.

For User defined, enter the Spring constant per unit area. This is a matrix K, coupling the displacements on the two sides.

Here, f is the force acting on the destination side, and Δu is the difference between the destination side displacements and the source side displacements. All vectors are expressed in the selected coordinate system.

Optionally, you can enter a Mass per unit area, ρu,A. This can for example be the mass of a glue layer.

For From Material, select a Joint material. The default is Boundary material, which is the material assigned to the destination boundary. You can also select any material defined in the component.

For Young's modulus, E, Poisson's ration, ν, and Density, ρ, the default is to take the values From material. You can also select User defined, and enter expressions for the material data manually.

When From Material is used, the gap between the two boundaries is used to compute the coupling stiffness, as if a virtual material is inserted between them.

In all cases, select the Source boundary and Destination Boundary — Top or Bottom. The information is used for two purposes: to connect to the correct set of displacements, and to compute the distance, including the shell thickness and offset.

The two boundaries are only connected if they are within a certain tolerance from touching each other. The distance is computed including shell thickness and offset, as well as the selected connection boundaries. You can modify this tolerance. Select a Connection tolerance — Automatic or User defined. For User defined, enter the maximum allowable distance or overlap between the boundaries, δ.

To display this section, click the Show More Options button () and select Advanced Physics Options in the Show More Options dialog box. The information in this section i sonly used if Method is set to Rigid.

Physics tab with Shell selected: