The In Situ Ply Shear Strength Distributions in Graphite/Epoxy Laminated Composites

Abstract

An experimental and analytical investigation was performed to study the in situ ply shear strength in fiber-reinforced laminated composites. The effects of ply orientation and laminate thickness on the ply shear strength in laminates were the major concerns of the study. T300/1034-C Graphite/Epoxy cross-ply laminates were selected for the tests, and a rail shear fixture was used for measuring ply shear strengths. A three-dimensional finite element program was also developed to analyze the interlaminar stress distributions in the specimens. The results of test data strongly indicate that the ply orientation and laminate thickness significantly influence the in-plane shear strengths of the laminates. This effect could be attributed to the inherent flaws introduced during manufacturing processes and to interlaminar stresses in laminates. As a consequence, ply shear strength should not be regarded as an intrinsic property of fiber-reinforced laminates. Due to the free edge effect, the results of shear strength distributions measured from the rail shear fixture were conser vative.