DEVELOPMENT OF AN INTRALAMINAR SHEAR FIXTURE FOR THE TESTING OF COMPOSITE SPECIMENS OUT OF THEIR ORTHOTROPY AXES

The design of innovative ceramic matrix composites parts requires a precise characterization of the materials to avoid oversizing costs. Several methods already exist to characterize the shear properties of composite laminates, classically the tensile tests on ±45° balanced specimens (EN 6031), known for their effectiveness. However, sampling specimens directly from parts or structures restricts the ability to select ply stacking sequences. Out-of-orthotropy-axes tests on unidirectional composite specimens allow for shear properties determination, but the stress state in the specimens is highly heterogeneous [1] [3], affecting measurements quality, especially for shear fracture stresses. Rotating fixtures have been developed to mitigate edge effects due to clamped jaws [2] [3] and homogenize the stress state in the specimens, but cannot reach high levels of stress. A double ball-jointed fixture for intralaminar shear testing of composite unidirectional specimens is hereby introduced. The in-plane rotations allow to limit the stresses heterogeneity one can observe in out-of-orthotropy-axes testings with clamped jaws. A comparison between a clamped-jawed tensile test on (±45°)ns stackings, and tests performed on the developed fixture with off-axis UD specimens is proposed to validate the method.