Determining Shear Moduli of Orthotropic Composites

Torsion tests on specimens of same orthotropic composite material having at least two different thicknesses enable determination of effective in-plane and out-of-plane shear moduli. Moduli are calculated from experimental data with elasticity-theory equations that relate applied torque, torsional twist angle, specimen width/thickness ratio, and ratio of two shear moduli. Tests were developed to yield information on degratation of properties of composite saturated by moisture.