The V-Notched Rail Shear Test

A V-notched rail shear test has been developed for measuring the shear modulus and shear strength of composites and other materials. This test method, standardized as ASTM D 7078, incorporates attractive features of the existing Iosipescu and two-rail shear tests. The V-notched rail shear specimen provides a larger gage section than the standard Iosipescu shear specimen and provides enhanced loading capability compared to either existing test method. Results from finite element analysis show that the V-notched specimen design reduces shear stress concentrations near the rails and produces relatively uniform shear stress distributions in the specimen gage section for a variety of carbon/epoxy laminates. Mechanical testing results from six carbon/epoxy laminates demonstrate excellent gripping performance using the V-notched rail shear test fixture and acceptable gage section failures. Additionally, results suggest that the use of [0/90] ns cross-ply laminates is preferred over [0] n unidirectional laminates for characterizing the lamina shear properties of composite materials.