Membranes for 3D Models
The Membrane interface in 3D can be active on interior and exterior boundaries of a domain, as well as on boundaries not adjacent to any domain.
The dependent variables are the displacements u, v, and w in the global x, y, and z directions, and the displacement derivative unn in the direction normal to the membrane. For anisotropic materials, the tangential displacements derivatives u1n and u2n are additionally added as dependent variables.