Modeling RVE with Interfaces

Hi All,

I am worling on developing an RVE (with interface) for a ceramic composite material. Interfaces are not load carrying members but help in increasing the fracture toughness of the material by deflecting a propagating crack into the interface. Because the interface does not help in load carrying, while we apply load (or displacement) on the RVE, should we apply it on the interface too? Here, I am applying a tensile load and I want to see matrix cracking followed by interface failure and then fiber failure. If load is applied on interface, then the stresses in interface are primarily tensile. But interface should fail in shear. 

Can anyone help with appropriate boundary conditions?  Any references?