Modeling Short-Beam Shear in Abaqus

Hi All, 

I am trying to model a short-beam shear specimen in Abaqus to understand the variation of interfacial shear. A short-beam shear specimen is essentially made of two individual halves (of polycarbonate, say for example) bonded together by an adhesive at the interface (can be without bonding as a single material too). It is then tested using an Iosipescu fixture to measure the shear across the interface. Additionally, I have a pre-crack with a/W=0.5 and I model the specimen using Abaqus. I use a seam crack (in Abaqus) for this purpose. But due to the shear involved, there is mesh overlap/crack interpenetration and I get negative SIF values. How do I avoid this? I have tried using interactions and hard contact, but to no avail. Also, I was wondering, if there is contact between the crack lips, then there must be friction involved which makes the problem more complex. Will using a 'hard contact' interaction property be justified in such a case? Please provide your valuable comments. 

-Arun