Deformation Gradient in VUMAT

Hey,

How can we use Deformation gradient in VUMAT abaqus explicit subroutine?

I am modelling user defined composite material. I have isotropic and anisotropic material properties in the model. For Isotropic model I have solved my equations using Stretch tensor but for Anisotropic model I need deformation gradient or If I can get rotation tensor and that can be multiplied with stretch tensor, not sure though.

Can anyone please help me, I am really badly stuck:(

The deformation gradient tensor is actually provided in VUMAT as DEFGRADNEW