Non-symetric laminate

[ezquerra]

I have a non symetric honeycomp, with different plies. I would like to check that the results of the ply stresses obtained in Nastran are correct, taking in count that I have introduced no offset in the PCOMP, so the reference plane and the neutral axis are different.

 

[vorwald]

One way to check the validity is to compare with the ABD matrices.

PCOMP uses matrices that are proportional to the A, B, and D matrices. The resulting PSHELL points to the following four material stiffness matrices;

MID1 which is A divided by plate thickness (T),
MID2 which is D divided by plate inertia (T^3/12)
MID3 which is a transverse shear 2x2 material stiffness matrix,
MID4 which is B divided by T^2

Warning: if you are applying thermal gradients to an unsymmetric layup, then the Nastran composite MIDi numbering scheme used must be followed if you are creating the MAT2 A terms for the above matrices yourself.
Otherwise you can use any numbers for the MAT2 ids.

 

[pbd999]

Does anyone know how Nastran calculates the MID3 transverse shear properties that go on the associated MAT2 card? I realize that you could leave this blank if you were creating the equivalent PSHELL by hand, but Nastran creates it for every PCOMP/MAT8 layup.