Rationale

Shear modulus is invariant in all directions for isotropic materials; however, shear modulus is planar property for orthotropic materials having a unique value for each orthogonal plane. E143 aggregates shear modulus values in a manner that results in a single value for a particular material axis loaded in torsion. This aggregated value is important for particular applications, such as power transmission shafts. However, directional nomenclature should be introduced in a manner consistent with B769, B831, and E238.