Modeling 2D orthotropic material in Nastran

I'm modeling a laminated composite surface in Nastran. In order to model the laminate, I need to define a 2D Orthotropic material (i.e. a
fiber/matrix composite). Nastran's asking for E1, E2, G12, G1Z, G2Z, and nu12 (Poisson's). In all the calculations I'd done for fiber/matrix composites in the past, I've only needed E1, E2, G12, and nu12. For long, continuous aligned fiber composites, should I leave G1Z and G2Z as 0?
Thanks in advance! Dave
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The requirement of G1Z and G2Z stem directly from the use of Mindlin plate theory with allowance for transverse shear. You can easily estimate them from a rule of mixtures, assuming the matrix and fiber fractions being parallel springs. As a result the G1Z and G2Z will be close to the G of the matrix material.
Timo

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dave.harper wrote:

If you set them to 0 or leave them blank the transverse shear stiffness will be infinite (rigid) like a regular beam.
If you want to estimate values, then use something that's a fraction of G12 since the matrix material dominates in the off fiber directions.
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