“…In strength of materials, we have learned the following formulas for beams made of a single isotropic material: (16) with EA denoting the extension stiffness, GJ the torsion stiffness, and EI 2 and EI 3 the bending stiffness about x 2 and x 3 , respectively. It is also noted here for a single isotropic material, E is the Young's modulus, G is the shear modulus, A is the cross-sectional area, J is the torsion constant, and I 2 and I 3 are the area moments of inertia about x 2 and x 3 , respectively.…”