The Effect of Testing Methods on the Shear Strength Distribution in Laminated Composites

Abstract

An experimental investigation was performed to study the effect of testing methods on the in situ shear strength distribution in fiber-reinforced laminated composites. T300/976 Graphite/Epoxy cross-ply laminates were used in the tests, and rail shear, Iosipescu, and short beam shear fixtures were selected for measuring the shear strengths. The results strongly indicate that the interlaminar shear strength measured from the short beam shear test has no correlation with the inplane shear strengths measured by the other two methods. The rail shear and losipescu fixtures provide, in general, consistent results in the measurement of the inplane shear strength. However, the consistency between the results of the two test methods strongly depends on the ply orientation of the test specimens. As shown in the paper, the resultant differences in inplane shear strengths measured from the two test methods could be as much 50%. These differences can be attributed to the in terlaminar stress distributions along the free edges of the specimens. Overall, the losipescu shear fixture produced lower shear strengths than the rail shear fixture.