Equivalent modulus for composite plate?

[floch]

Hi,

"first,Sorry for the mistakes"

I begin in analysis composite and i want calculate the equivalent modulus of the plate composite(carbone/epoxy) (sequence.0°,45°,0°).


I calculate the global stiffness matrix (A, B, and C)
i found a formul in composite stress manuel to calculate the equivalent modulus. For exemple, for Exx

Exx=(A11*A22-A12^2)/A22*h

with h tickness of the plate

The result is good for me with this sequence but when i increase the plies number, the Ex and Ey modulus decrease and vice versa.

i find it's strange.I think this formulation isn't correct but i don't found the mistakes.

Can you help me please.Thanhs

 

[SWComposites]

The formula appears correct

Ex = 1/(a11*h)

where [a] = inv[A]