Use of DIC in the characterisation of mode II crack propagation in adhesive fatigue testing

Adhesively bonded joints are used in many applications which are dynamically loaded. Thus, excellent fatigue properties of adhesives, especially under fracture mode II, are required. The fracture mode II testing of adhesive is challenging, where the observation of the crack length is complicated. Accordingly, compliance-based effective crack length definitions avoiding direct observation have been used instead. The experimental crack monitoring method using digital image correlation (DIC) is studied in this work. The DIC-based monitoring is compared to the compliance-based method in defining the crack length. The developed DIC-based method is useful to study, especially, the microcracked adhesive region ahead of the distinct open crack tip.