# Orthotropy

### Glossary Term

Orthotropy describes directional material properties.

Examples for this are fiber-reinforced plastics, trapezoidal sheets, reinforced concrete or timber. As a rule, the Hooke's material law ($\mathrm\nu\;=\;\frac{\mathrm E}{2\;\cdot\;\mathrm G}\;-\;1\;\leq\;0.5$)  is not valid for orthotropic materials anymore.

###### Material Parameters

For a 2D shell element, the material parameters are as follows:

• Ex stiffness in the local x-direction of the surface
• Ey stiffness in the local x-direction of the surface
• Gxz shear stiffness in the local x-direction of the surface
• Gyz shear stiffness in the local y-direction of the surface
• Gxy shear stiffness in the wall plane