Effective in-plane Poisson’s ratio :
Let us define this Poisson’s ratio as follows

(5.74)

Using the first and second of Equation (5.71) we can write

(5.75)

Coefficient of mutual influence of first kind :

Let us define the coefficient of mutual influence for the loading in Equation (5.70) as

(5.76)

For the second and third of Equation (5.71) we have

(5.77)

In-plane effective shear modulus :

Let the loading on laminate be

and

(5.78)

Thus, for this loading we can write from Equation. (5.59) as

(5.79)

Let us define the inplane effective shear modulus for laminate as

(5.80)

With the use of Equation (5.79), we can write

(5.81)