FYI: I'm running SolidWorks 4.1
1 Geometry : You can cut out 3/4 of geometry and use Symetry to reduce number of elements and reduce total number of contact points,
2 Contact : Ensure if node2node definition is what you want. Isnt that so, that middle layer shall slide surface on surface to expand under given pression?
I checked your model, you did not applied proper boundary conditions for the parts.
You applied the normal load on the top plate, what about the constraints to that plate. if you are not applying any constraints means it can move in any direction.
you need to arrest the top plate remaining two directions i.e. allow the top plate move in downward direction only.
before running the nonlinear analysis, first solve the problem in static analysis with the applied boundary conditions. if its solving means then solve the same problem with nonlinear analysis i.e. changing the material, time curve etc.
kindly let me know if i am wrong.