# Membrane elements

 Membrane elements are sheets in space that can carry membrane force but do not have any bending or transverse shear stiffness, so the only nonzero stress components in the membrane are those components parallel to the middle surface of the membrane: the membrane is in a state of plane stress. The following topics are discussed:
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ProductsAbaqus/StandardAbaqus/Explicit

At any time we use a local orthonormal basis system $ei$, where $e1$ and $e2$ are in the surface of the membrane and $e3$ is normal to the membrane. The basis system is defined by the standard convention used in Abaqus for a basis on a surface in space. In this section Greek indices take the range 1, 2, and Latin indices take the range 1, 2, 3. Greek indices are used to refer to components in the first two directions of the local orthonormal basis (in the surface of the membrane).