This parameter can be used only if the USER parameter is specified.

Set this parameter equal to the number of property values needed as data in user subroutine VFABRIC. The default value is 0.

You can introduce state variables using the *DEPVAR option and update these variables within user subroutine VFABRIC. You can delete the element, if needed, using one of these state variables.

Set STRESS FREE INITIAL SLACK=YES (default) to generate zero stresses in regions under initial compressive strains along the fill and the warp directions (these initial compressive strains may arise from modeling techniques such as the initial metric method—see *INITIAL CONDITIONS, TYPE=REF COORDINATE). The stress remains zero as the strain is continuously recovered from the initial compressive values toward the strain-free state. Once the initial slack is recovered, any subsequent compressive strains generate stresses as per the material definition.

Set STRESS FREE INITIAL SLACK=NO to generate stresses in the initial configuration as per the material definition even over fabric regions that are under compressive strains.

Abaqus also offers a technique to introduce any initial stresses, both tensile and compressive, in fabric materials gradually over a specified time period (see *SECTION CONTROLS).

Include this parameter if the fabric stresses in a local system are updated in user subroutine VFABRIC given the total and the incremental fabric strains in the local system.

If this parameter is omitted, you must include the *UNIAXIAL option to define the fabric response using test data in terms of the fabric stresses and the fabric strains in the local system.

The local system for the fabric material defined either through the test data or the user subroutine is initialized to the fill and the warp yarn directions in the reference configuration by using the *ORIENTATION option. Abaqus updates this local system with deformation to track the fill and the warp directions in the current configuration.