Correlation of three standard shear tests for unidirectional glass-epoxy composites

The shear strength of unidirectional glass-epoxy composites was determined experimentally by three standard shear tests. The tests consisted of short beam interlaminar shear tests, saw-cut shear tests, and torsion tests on circumferentially wound cylinders. Test results show that the short beam interlaminar shear tests and the torsion tests of circumferentially wound cylinders give approximately the same maximum shear stress. Test results also showed that the saw-cut shear test is not a good interlaminar shear test because of stress concentrations at the base of the saw cuts and high tearing stresses normal to the plane of shear. The shear strength determined by the beam and torsion tests is approximately 10 ksi, whereas the average shear strength for the saw-cut specimens is approximately 2.5 ksi.