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NASTRAN PCOMP

NASTRAN PCOMP

NASTRAN PCOMP

(OP)
I'm trying to take a NASTRAN deck with a honeycomb panel modeled with a PSHELL and MAT1 cards and change it to a PCOMP card with MAT8 cards.  The PSHELL was modeled following the NASA FEMCI procedure and the results match hand solutions.  When I change the deck to PCOMPs with each section being its own ply ( 2 face sheets and a core for a total of 3 plys) I get membrane reactions down loading at the boundaries where the PSHELL only gets corresponding up loads, lower stresses and lower deflections.  I thought NASTRAN was supposed to take the PCOMPs and make PSHELLs.  Anyone know why I'm getting those reactions?  Could it be a cross coupling of the Matrix or a Poisson effect?  Thanks

RE: NASTRAN PCOMP

Nastran outputs the internally generated PSHELL/MAT2 cards to the .out/.dat file.  Depending on what version of Nastran you are using, you may have to turn on a flag/parameter to get the cards written to teh output.  I suspect the problem you are having is due to differences in 1) transverse stiffness, 2) coordinate systems.  What vendor/version of Nastran are you using?  I you still can't figure it out, post your PCOMP and PSHELL cards here.

RE: NASTRAN PCOMP

(OP)
Here is my PSHELL and Mat1 cards
PSHELL         1       1    0.04       1   468.8       2     12.      0
MAT1           11.06E+07            0.330.000259      0.     70.        +MT    1
+MT    1      0.      0.      0.
MAT1           2 113400.            0.89              0.     70.        +MT    2
+MT    2      0.      0.      0.

My PCOMP MAT8 is follows:
MAT8           11.060E+71.060E+7    0.333900000.  39000.  39000.0.000261
MAT8           5      1.      1.    0.89      0.  29800.  66000.6.44E-06
PCOMP          1    0.250.000161                                            
               1    0.02      0.      NO
               5    0.46      0.      NO
               1    0.02      0.      NO

I'm running MSC.NASTRAN 2005.  Thanks again

RE: NASTRAN PCOMP

1) it appears that the transverse shear stiffnesses are not the same.  I don't understand why on the PSHELL card Rt (Ts/T) = 12.
2) a value of 0.89 for poisson's ratio for the core does not seem realistic.  I would just set this value to 0 for a h/c core material
3) the Z0 parameter on the PCOMP card is incorrect.  It should be -0.25 or blank.

RE: NASTRAN PCOMP

(OP)
Thanks, Poisson's Ratio seems to have fixed the problem.

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