Shear Modulus of Aluminium Alloy

Applying G = E / [2(1 + ν)] with E = 68.9 GPa and ν = 0.33 gives 25.9 GPa, and NASA's 6061 data handbook gives a design value of 3.8 × 10⁶ psi (26.2 GPa). As with Young's modulus, temper and alloy move it by a couple of percent at most.

Aluminium's low shear modulus is a bigger practical problem than its low Young's modulus, because aluminium sections are typically thin-walled extrusions and thin walls are what torsion and shear buckling punish. A 6061 open channel resisting torque twists roughly three times as much as an identical steel one; shear-buckling and web-crippling checks that are formalities in steel become governing limit states in aluminium. Treat this value as isotropic room-temperature wrought material: castings are lower and less consistent, and everything softens above about 150 °C.