CQUAD4 in bending test

[O_Stodieck]

I have fixed the problem causing a crash with plate pressure load. Attached is a QUAD4 problem that you asked about. It is a thick plate and the bdf file is attached (you will have to change the extension as the forum would not allow .dat or .bdf). The theoretical thick plate solution for the max displacement is:

Max displacement: theoretical = 4.294E-07

Thanks Bill. I just ran the file and am getting a max deflection of 4.280877E-07, that seems fairly close to the theoretical, so no problems there.

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O_Stodieck, the book is "Practical Analysis of Aircraft Composites". The [d] properties are just from the [a], [b], [d] instead of the [A], [B], [D]. You can also use Exb (or Eby depending on the orientation) for this problem as well. All of those calculated in eLaminate here btw: https://www.espcomposites.com/software/download.html

Regarding the issue, we know that the isotropic is OK (so its probably not an element issue or general issue). I would first try just a MAT8 orthotropic material (no PCOMP) and make sure that is behaving properly. If so, then we can look that the PCOMP further. The fact that you said changing the ply angles had no effect may mean there is an issue. But first I would like to isolate the issue to either the MAT8 side (as a general orthotropic material, but not a composite) or the PCOMP side. Then I can take a deeper look into as well...but something seems odd. I have not used composites in MYSTRAN, but that is something we need to make sure is correct.

Thanks for the references. 

I tried 2 more approaches:

1. replacing the PCOMP with a PSHELL as suggested - the results are the same, i.e.  T3 = 3.613534E-02 (although a lot more information messages are generated, related to shear stiffness)
   
2. replacing the MAT8 with a MAT2, where the G matrix terms are calculated from [D]*12/T**3 - again the results are the same with T3 = 3.613380E-02.
   

So it looks like the error is not limited to MAT8 or PCOMP... (see input files attached)