In-plane Laminate Engineering Constants:

Now we express the laminate engineering constants with the help of thought experiments as follows.

Effective in-plane longitudinal modulus :

The state of stress applied is

and

(5.60)

For this state of stress, we get the relation as

(5.61)

Let us define effective in-plane longitudinal modulus as

(5.62)

Using Equation (5.61) we get

(5.63)

Effective in-plane Poisson’s ratio :

Let us define the effective in-plane Poisson’s ratio as

(5.64)

For the state of stress in Equation (5.60) we have

(5.65)

From Equation (5.61) and Equation (5.65), we can write for Equation (5.64) as

(5.66)