MAT2 2D Anisotropic Material 1

[StaffStress]

Hi all, I'm a frequent reader but this is the first question I've posted. I have severe confusion regarding stiffness values to use for MAT2 card 2D anisotropic manual material input in Nastran/Patran.

I need to evaluate a membrane material card and a bending material card for a particular laminate. The MAT2 input fields are G11, G12, G13, G22, G23, G33.

Nastran user guide is rather incomplete in defining the equations for the Gij values for membrane material and also for the bending material and which matrix, i.e. reduced stiffness or rotated reduced stiffness, to use. The literature typically defines these matricies as [Q] and [Q-bar] respectively and not as [G]. I asume for the bending material the [D] matrix must be involved??


Questions are, which of the stiffness matricies from CLT is appropriate to use for the Gij's (Qij or Qij-bar)?
How do the stiffness calcs for Gij differ for the membrane material vs. the bending material?
Regards.

 

[StaffStress]

Further research in the forums got my answer for the MAT2 membrane and bending material stiffnesses:

membrane stiffness: [A]/t
bending stiffness: [D]/(t^3/12)

P.S. Sorry for the cross posting... now realize it's against policy!

 

[Hansmeister]

You have correctly answered your own question. The "G" terms are placeholders.

Mat2 cards are used with Pshell cards. Membrane is [A]/t, and bending is 12*[D]/t^3. If there is membrane-bending coupling, then the matrix is also used; /t^2. Where [A], and [D] are the portions of the Constitutive Equation.

 

[StaffStress]

Thanks for the reply.
Assuming a membrane-bending coupled laminate, in terms of material property definition on a MAT2 card, how would the terms be incorporated in addition to membrane material stiffness and bending material stiffness?

 

[Hansmeister]

Look up your Pshell data fields.

Mid1 is the membrane matrix,

Mid2 is the bending matrix,

Mid3 is the honeycomb or foam core matrix (if used),

Mid4 is the coupling matrix (which means the laminate is not symmetric about the midplane).

Where, Mid? references the Mat2 (or Mat8) cards with the 5 terms of the material properties matrix, except for Mid3 where only two terms are used. For Plane Stress problems, Mat2's work for me.

 

[StaffStress]

Yes, ok - PSHELL MID4 pointing to MAT2 MID4 with the /t^2 terms.