Three-dimensional crack surface evolution in mode III delamination toughness tests

The three-dimensional evolution of a delamination and multiple coupled transverse cracks is studied in laminated tape composites using different mode III tests and specimens. All combinations produce 45° transverse cracks that initiate at the delamination front prior to delamination advance. For unidirectional laminates, the transverse crack length is governed by thickness, whereas for multidirectional laminates the transverse crack length is controlled by the ply angle and stacking sequence. These and other details of laminate architecture are shown to dictate the crack surface evolution, and provide distinguishing characteristics between the different laminates tested as well as in comparison to homogenous materials.