Modelling of a cut in a composite-laminated pressure vessel

[boeri]

Does anybody has some experience with the finite element simulation of a cut (not a crack!) in the laminate of a carbon fibre/epoxy tank under internal pressure? The intention of the finite element model is to make a comparison between a tested construction (damaged CFRP tank under internal pressure upon burst) and the model. This to make prediction possible. I used thick shell quad elements for the cylinder. I want to simulate a cut in axial direction and one in hoop direction. The laminate (from inside to outside = [90/90/0/0]). So both type of cuts will be in the helical layer(s) and maybe slightly through the hoop layers, depending on the depth of it. At the position of the cut, I refined the mesh until the width of the elements equalled the width of the cut. The material property of the cut-elements was also altered: it has two outer layers made from a very low stiffness material instead of CFRP.
The problem now is that I cannot trust the results, because of the large strain gradients, perpendicular to the direction of the cut. They differ more than 10% between two nodes in the same element.
Anybody any advice how to ameliorate my model to obtain a more realistic model?

All help is appreciated!