Torsion testing for shear modulus of thin orthotropic sheet

Abstract

O materials have nine independent elastic constants, of which three are shear moduli for three orthogonal planes. The simpler transversely isotropic materials have five distinct constants, of which only one is a shear constant, the remaining shear properties being determined by the uniaxial moduli. In each of these material classes shear tests are required to evaluate completely the elastic constants, and methods are needed for extracting these constants from test data. Although a procedure is available for obtaining all the elastic constants bf orthotropic materials from a series of uniaxial tensile or compression tests alone such a method requires that the tests be made in a wide variety of orientations. For thin sheet this is not possible, but torsion tests provide a suitable alternative. Although an analysis of orthotropic torsion has existed since the last century no practical use has been made of it, with the significant exception of the work of Trayer and March who studied the behavior of wood. This Note demonstrates a method of shear testing and of data reduction based on the torsion analysis which can be used for obtaining the elastic shear constants of thin orthotropic sheets. The method has been applied to a study of a cross-rolled beryllium sheet.