NASTRAN PCOMP 1

[nachomano5]

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

 

[SWComposites]

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.

 

[nachomano5]

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

 

[SWComposites]

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.

 

[nachomano5]

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