Abaqus / polymer simulation

Hi all,

I'm trying to model a peel T test on a composite material composed of steel and polymer (polypropylen) on Abaqus 6.7. Between these parts, there are cohesive elements COH3D8.
I have a problem with my model and I don't understand it. You can visualize my results in attachs files.
For understand this draw, a few precisions:
The elements in white has just here to guide the materials.
In B (cf attachs files), the nodes are embedded.
In A I applied a velocity.
In C I applied rotation constraints and coupling constraints on all rotations and displacements.
My structure present a strange evolution in the red circle. I don't understand this.

Have you an idea on what is happened in my structure? It is a problem of material? Maybe you have had the same problem...
If you need more precision on the model, the materials or limits conditions, I'll answer it of course.

Excuse my poor english.
Poucinette