from NASTRAN help ...
MAT2 Shell Element Anisotropic Material Property Definition
Defines the material properties for linear anisotropic materials for two-dimensional elements.
defines Gij such that stress_i = Gij*strain_j (i think !?)
field3 = G11,
field4 = G12,
field5 = G13,
field6 = G22,
field7 = G23,
field8 = G33
and MAT8 Shell Element Orthotropic Material Property Definition
Defines the material property for an orthotropic material for isoparametric shell elements
field3 = E11 = G11 (ie field3 from MAT2)
field4 = E22 = G22 (ie field6 from MAT2)
field5 = nu12 = G12/G11 (MAT2 field4/field3)
field6 = G12 = G33 (ie field8 from MAT2)
field7 = G13 = field5 on MAT2
field8 = G23 = field7 on MAT2
i tried to copy the manual, but the tables wouldn't show properly.
GL