Example 5.7: Consider Example 5.3. Let this laminate be subjected to the forces ,  and . Calculate global strains and stresses in each ply.

Solution: The laminate in this example is a symmetric laminate. Hence, B matrix is zero. It means that there is no coupling between extension and bending actions. Thus, the applied stresses will produce only in-plane and shear strains and it will not produce any curvatures. Thus, it is easy to understand that the mid-plane strains will be the strains in each ply.

We can find the mid-plane strains as follows:

The strains are same in all layers. However, the stresses in each layer will be different as their stiffnesses are different.

Stresses in  layer are

And stresses in  layer are

Now, let us find the strains and stresses in principal material directions as well for these laminae.

Let us transform the strains in  layer as

Similarly, the strains in  layer in principal directions are

Now, stresses in principal directions in  layer are

And stresses in principal material directions for  layer are