Composite Shear Moduli and Strengths from Torsion of Thick Laminates

Composite bars of rectangular cross sections are loaded in torsion to determine the principal shear moduli and interlaminar strengths. The use of rectangular cross sections greatly simplifies the fabrication of specimens. In [0], [90], and cross-plied laminates, torsional rigidity depends only on the principal shear moduli and the dimensions of the cross section. Thus, the shear moduli can be determined from the measured torsional rigidity. This procedure proves very accurate and convenient in determining the transverse shear modulus G₂₃. The use of this technique to measure in-plane shear and interlaminar strengths is also discussed in this paper.