umat -jacobian computations Help please

[Umat]

Dear Abaqus users,
         The Task which i am doing(Progressive damage modeling of 3D composites), Had some problems dealing with Jacobian computations.
For reference you can look at

http://ol.cadfamily.com/ABAQUS/Documentation/docs/v6.6/books/exa/default.htm


For the 2 d plane stress model which we had in the documentation says
                  S=Cd*eps, where S is stress, Cd is damaged stiffness matrix and eps is  strain. The Jacobian has the form:

d(S)/d(eps) = Cd+d(Cd)/d(D_k)*d(D_k)/d(eps),

But for 3 D structures can we compute it in the below form

d(S)/d(eps) = Cd+d(Cd)/d(D_k)*d(D_k)/d(eps),


computing d(Cd)/d(D_k)  ie stiffness matrix wrt three damage variables is not a problem in computing
but
computing d(D_k)/d(eps) is quite complex to do it
do you have any solution for it

what we had in the 2d model is
d(D_k)/d(eps)= d(FLT)/d(eps) * d(D_k)/d(FLT)                                            where FLT is the Failure criterion condition
 
what does the above equation represents in physical sense
can we do the same procedure for 3D structures


Thanks for Sparing your time,
Rajesh