When
a sample is subjected to a tangential or shear force the stress is referred to as a shear stress, τ. The strain determined is referred to as shear strain γ. It is
defined as the displacement of one surface with respect to another divided by the distance between them (Figure 1): γ = Δx/y = tan θ.
Figure 1: Shear strain
The shear modulus G is defined as the ratio of shear stress and strain: G =τ/γ. The shear modulus G can be expressed as: G = E/2(1+ν), where E is the Young's modulus and ν is the Poisson's ratio.
