Effect of specimen size on interlaminar shear strength of unidirectional carbon fibre-epoxy

Abstract

A systematic study has been undertaken to investigate the effect of specimen size on the interlaminar shear strength of unidirectional carbon fibre-epoxy using the three-point short-beam shear test. By varying the test parameters such as the ratio of span to thickness and the diameter of the loading roller, it is found that a valid interlaminar shear failure mode can be obtained and thus the three-point short-beam shear test can be used as a reliable method to measure the interlaminar shear strength, at least on a comparitive basis. From tests on four sets of scaled specimens, a significant size effect is found in the interlaminar shear strength. However, the Weibull statistical model does not satisfactorily represent the size effect. The test results indicate that the Weibull modulus increases with decreasing size, and suggest that the strength is approaching a limiting value for small specimens.