Membrane Elements

You can define a constant section thickness as part of the section definition.

MEMBRANE SECTION, ELSET=name
thickness

Property module: Create Section: select Shell as the section Category and Membrane as the section Type: Membrane thickness: thickness

In Abaqus/Standard you can define a spatially varying thickness for membranes using a distribution (Distribution Definition).

The distribution used to define membrane thickness must have a default value. The default thickness is used by any membrane element assigned to the membrane section that is not specifically assigned a value in the distribution.

If the membrane thickness is defined for a membrane section with a distribution, nodal thicknesses cannot be used for that section definition.

MEMBRANE SECTION, MEMBRANE THICKNESS=distribution name

Alternatively, you can define a continuously varying thickness over the element. In this case any constant section thickness you specify will be ignored, and the section thickness will be interpolated from the specified nodal values (see Nodal Thicknesses). The thickness must be defined at all nodes connected to the element.

If the membrane thickness is defined for a membrane section with a distribution, nodal thicknesses cannot be used for that section definition.

MEMBRANE SECTION, NODAL THICKNESS
NODAL THICKNESS

You must associate a material definition with each membrane section definition. Optionally, you can associate a material orientation definition with the section (see Orientations). An arbitrary material orientation is valid only for general membrane elements and axisymmetric membrane elements with twist. You can define other directions by defining a local orientation, except for MAX1 and MAX2 elements (Axisymmetric Membrane Element Library), which do not support orientations.

In Abaqus/Standard if the orientation assigned to a membrane section is defined with distributions, spatially varying local coordinate systems are applied to all membrane elements associated with the membrane section. A default local coordinate system (as defined by the distributions) is applied to any membrane element that is not specifically included in the associated distribution.

MEMBRANE SECTION, MATERIAL=name, ORIENTATION=name

Property module: 
Create Section: select Shell as the section Category and Membrane as the 
section Type: Material: name
AssignMaterial Orientation

You can define how the membrane thickness will change with deformation by specifying a nonzero value for the section Poisson's ratio that will allow for a change in the thickness of the membrane as a function of the in-plane strains in geometrically nonlinear analysis (see Defining an Analysis).

Alternatively in Abaqus/Explicit, you can choose to have the thickness change computed through integration of the thickness-direction strain that is based on the element material definition and the plane stress condition.

The value of the effective Poisson's ratio for the section must be between −1.0 and 0.5. By default, the section Poisson's ratio is 0.5 in Abaqus/Standard to enforce incompressibility of the element; in Abaqus/Explicit the default thickness change is based on the element material definition.

A section Poisson's ratio of 0.0 means that the thickness will not change. Values between 0.0 and 0.5 mean that the thickness changes proportionally between the limits of no thickness change and incompressibility, respectively. A negative value of the section Poisson's ratio will result in an increase of the section thickness in response to tensile strains.

MEMBRANE SECTION, POISSON=${\nu }_{\mathrm{eff}}$
MEMBRANE SECTION, POISSON=MATERIAL (available in Abaqus/Explicit only)

Property module: Create Section: select Shell as the section Category and Membrane as the section Type: Section Poisson's ratio: Use analysis default or Specify value: ${\nu }_{\mathrm{eff}}$