Thanks for the previous answer.
I have the last thing to clarify. Lets assume pure in plane tension. When I build up a simple stacking -45/90/45/0 (same material used for each layer), in the Enginering Constants I get (with Poissons) different stiffness values in longitudinal and transverse direction. Ex=16000, Ey=9300.
Simillar confusion is when I create -45/90/45/0/0/45/90/-45 and 0/45/90/-45/-45/90/45/0. In the first case Ex=10000, Ey=18500. In the second case Ex=27000, Ey=12000.
Could you please shortly explain the ground of that behaviour? It might be basics i have overlooked, but its better to ask.