I have read many publications using FE model to study interfacial behaviour. And Few of them considered matrix viscoelastic effect in the studies. I seems that most authors avoid to discuss about this.
I think there are, e.g. Article Effect of Linear Viscoelasticity on Stress Transfer in a Num...
If you cannot find something you think it should be considered but actually not -- it may not make sense, may be too hard or people have not been that stage. If you believe it is important, than your chance is there -- go and do it