3D observation of delamination in carbon-fibre-reinforced composites under mode II loading through in situ computed tomography

Delamination is among the most prevalent life-limiting failure modes in laminated composites. Mode II delaminations, driven by in-plane shear loads, are more difficult to observe than mode I delaminations. Conventional edge observation techniques fail to capture the three-dimensional (3D) delamination front and its associated damage mechanisms. We conduct the first in situ X-ray computed tomography (CT) experiment to observe the 3D development of delamination under mode II loading. We apply four-point end-notched flexure loading to two types of thin-ply, carbon-fibre-reinforced composite laminates: a 0° laminate and a cross-ply laminate susceptible to delamination migration. The method is proven capable of capturing delamination growth and migration within the bulk of the laminates at the meso- and microscale, something unattainable using conventional techniques. This work thus demonstrates the benefits of in situ CT in determining the damage mechanisms involved in mode II fracture loading.