Composite Layup orientation problems

Hello everyone,
 I am doing a 3 layered composite beam using composite layup (fibre) for top and bottom layers. I have set a custom datum csys for both top and bottom layers with varying orientation angle. I was trying to obtain the result varying for 0, 30, 45, 70, and 90 degree orientation angle. The higher the orientation angle, the frequency result should be lower. However the result of the frequency I obtained for 0 degree and 90 degree are the same. As well as 30 degree and 70 degree. It seems like the results I obtained are symmetry.
 Hope anyone can help. Thank you.