A new curvature‐driven delamination test for measuring the mode II toughness of composites

Abstract The measurement of the delamination toughness of composites requires fracture tests with well‐characterized geometries. Because the delamination toughness is frequently used as a material selection parameter, it is necessary to differentiate between experimental artifacts, data scatter, and changes in the mechanism of delamination. This new Curvature‐Driven Delamination (CDD) test for Mode II provides a direct, steady‐state measurement of the pure Mode II delamination toughness without the compliance calculations inherent in other delamination test protocols. Like the Wedge‐Driven Delamination (WDD) test for Mode I, the CDD Mode II test measures the toughness at controlled crack growth rates. The CDD Mode II test correlates well with the results of the established End‐Notch Flexure (ENF) Mode II test but is not subject to the geometric instabilities of that test. Changes in the delamination mechanism are easily observed by the direct, continuous measurement of the toughness in the CDD Mode II test.