The Wyoming-modified two-rail shear test fixture for composite materials

A significantly modified two-rail shear fixture with a new clamping concept and enhanced gripping capability has been designed, fabricated, and evaluated. This new fixture solves some of the major shortcomings associated with the ASTM Standard D 4255 Two-Rail Shear test procedure, including limited specimen gripping ability, the need for specimens with holes, and potential failure by out-of-plane buckling. The in-plane unidirectional ply shear properties of AS4/3501-6 carbon/epoxy were measured using specimens of [0/90](3S) cross-ply orientation. Repeatable results and acceptable failure modes were obtained. The excellent gripping capability of the new test fixture was also demonstrated in tests of an AS4/3501-6 carbon/epoxy [+/-45](4S) angle-ply composite, a very high shear strength material.