2. Shear Of an Off-Axis Lamina:

In similar way to the tensile testing of a laminate one can use a unidirectional off-axis tensile coupon to determine the shear response of a composite in the principal material coordinates. A tensile test on off-axis lamina is a commonly used. Specimen has same geometry as in Figure 8.9. The state of stress in principal material coordinate directions can be obtained from transformation relations. Since, the shear response in the principal material coordinates is uncoupled from the normal response we can write the shear modulus as

(8.21)

The shear stress in the principal material directions due to axial tensile stress can be given using transformation relations as

(8.22)

The shear strain is measured from the strains    and  with the help of strain transformation relations. Then the apparent shear modulus    can be given as

(8.23)