Monitoring crack tip position in Cracked Lap Shear specimens subjected to fatigue loading

In recent years, interest in adhesively bonded joints has significantly grown, as it offers numerous advantages with respect to other joining techniques. Bonded joints are being increasingly adopted in structures subjected to fatigue loading, which might initiate and propagate crack-like debonding defects. The ability to detect and locate these defects is crucial for increasing overall safety. This study aims to investigate the capability of two commonly used Non-Destructive techniques, namely Digital Image Correlation and Visual Testing, to correctly locate the crack tip of a debonding damage. For this purpose, a specific Cracked Lap Shear specimen, which features mixed mode I-II loading conditions, was designed, manufactured, and tested under fatigue loading. Two different adhesives were used. The results showed that Digital Image Correlation was able to easily identify the crack tip, while visual inspection proved to have some difficulties due to the prevalence of mode II, which makes crack identification more troublesome.