Numerical and Experimental Assessment of a Modified Transverse Cut Tension (TCT) Specimen for In-Situ Loaded X-Ray Computed Tomography of Mode II Dominated Composite Damage Progression

The principal means by which delamination may progress in appropriately designed composite aerospace structures is via Mode II fracture. This can arise near bolted and bonded joints, following in-service damage such as impact or following the inclusion of integrated electronics into the composite structure and manufacture-induced defects. A new specimen type based on the Transverse Cut Tension (TCT) test is proposed to allow the use of in-situ X-ray micro-computed tomography for observation of mode II fracture processes. The tomography seeks to non-destructively observe the progression of three dimensional crack front features that cannot be seen in typical aerospace composite tests. The paper comprises an account of the design using analytic and finite element methods and preliminary experimental verification. The results showed that the measured toughness of the miniaturized specimen compared well with published results for this material in the literature. In addition, a small period of stable fracture growth was found that would permit in-situ X-ray micro-tomography of progressing Mode II cracks. The work provides the means to observe three-dimensional Mode II crack fronts, potentially in the presence of friction effects, which will contribute to establishing a firmer basis for improved physics-based simulation development.