Simulation sandwich structure ANSYS Mechanical

[COLOR=#333333][FONT=PT Sans]Hello everyone![/FONT][/COLOR]
[COLOR=#333333][FONT=PT Sans]I’m using APDL to simulate the behavior of a specimen in tension with a sandwich structure made of honeycomb and glass fiber. It was modeled in CATIA V5 and exported to APDL in a parasolid file. Only a half of the structure has been modeled because of symmetry condition. [/FONT][/COLOR]
[COLOR=#333333][FONT=PT Sans]NOTE: Some relevant images are submited in the attached file.[/FONT][/COLOR]

[COLOR=#333333][FONT=PT Sans]The specimen has a stepped repair, formed by five layers of glass fiber, each of these layers has been modeled individually, with the same directions as the parent material [0-90], and glued together with contacts through MPC approach, the same as the rest of the specimen, everything has been bounded with contacts. The type of analysis is static-structural, the load tension is transmitted through nodes by a piece of Aluminium joined by adhesion to the sandwich structure. The boundary conditions applied in the model are:[/FONT][/COLOR]
[COLOR=#333333][FONT=PT Sans]The load has been applied on the left edge of the specimen, that is representative of the Aluminium plate, also, all the DOF has been restringed, except for the displacement on the “x” direction which corresponds to the direction of the applied tension load. The other edge has symmetry conditions and a restriction on the “z” direction (transversal direction).[/FONT][/COLOR]

[COLOR=#333333][FONT=PT Sans]The hole specimen has been modeled with SOLID185, solid and layered elements, furthermore, most of the volumes have been divided with the purpose of get a regular mesh with a low quantity of wedge elements (less than 1%), after that, they were glued again with Boolean operator VGLUE. I have some troubles getting accurate results from the behavior of this model. [/FONT][/COLOR]

[COLOR=#333333][FONT=PT Sans]There are no relevant warnings before I solve the model, but it always appears a large pivot when I try to get the solution. The behavior of the deformed shape I obtain is totally different as I expect, because it seems that some parts of the laminate have debonded. I’ve checked for overconstraints or an underconstrained model, but all seems to be ok. I also have tried with different approaches for the contact technology such as Lagrangian method or penalty method, but I get the same problem for all of them. I also have applied a first load step with very small displacements to obtain convergence, and for the second step, the enforced displacements have been removed and the force required has been applied, but, even though the displacement at the first load step is very small, there is a pivot in the solution. I found another trouble when I check the behavior of the deformed shape of the model, despite I only applied a tension load, firstly I get compression behavior, followed by tension, and I don’t know why that’s happening. [/FONT][/COLOR]
[COLOR=#333333][FONT=PT Sans]I’d really appreciate your thoughts on the matter.[/FONT][/COLOR][IMG]http://www.engineersedge.com/engineering-forum/attachment.php?attachmentid=1419&stc=1[/IMG][IMG]http://www.engineersedge.com/engineering-forum/attachment.php?attachmentid=1420&stc=1[/IMG][IMG]http://www.engineersedge.com/engineering-forum/attachment.php?attachmentid=1421&stc=1[/IMG]

It appears that you are primarily convinced that there is an analysis issue rather than a potential issue due to the repaired component structure. It would be helpful to see illustrations of your analysis results including the the folding effect you describe.