Cohesive Zone Modelling Problem

[KostasNik]

Hello,

I use Patran/Nastran 2014 and I am trying to create a 2D DCB model for delamination analysis using Cohesive zone elements. The adherents are of the same isotropic material. When I create the 2D solid properties I use Plain Strain, Standard Formulation for the adherents and Plain Strain, Interface for the adhesive. The problem is that the .bdf file created contains PSHELL properties instead of PLPLANE as I whould expect it to. However the model gives results (Implict Nonlinear analysis, 100steps). Is there any reason that this is happening?

In detail:
1. For the adherents
Object: 2D
Type: 2D solid
Plane Strain
Standerd Formulation
As material the isotropic material previously created
Plane of Deformation: Coord 0
Output Locations: Gauss
Nonlinear Formulation: Automatic

2. For the Adhesive
Object: 2D
Type: 2D solid
Plane Strain
Interface
As material the cohesive material previously created
Interface Integration Scheme: Gauss
Output Locations: Gauss
Stiffness Matrix Scheme: Secant
Thickness: 1 **

**The thickness of the Cohesive zone in the geometry of the model is 0.15mm. Should I leave the space blank, fill in 0.15 or 1 as default value? Also what is a credible thickness value for this type of modelling? Is the vertical translation of the nodes above the lower adherent, in order to create a zero thickness of the CZM, a better way?

Thanks in advance!