If you are using a material that has isotropic or anisotropic matrix data, select from the drop down list, then select to display the Matrix properties dialog to edit the matrix properties.
When you use matrix properties with materials that have anisotropic matrix data, the Mori-Tanaka micro-mechanics model will be used by default.
If you select , or if you select with materials that have isotropic matrix data, the Tandon-Weng micro-mechanics model will be used by default.
is included for backward compatibility with old study files.