The challenges of quasi-static and fatigue experiments of structural adhesives

This paper presents the results of an experimental campaign designed specifically to investigate unexpected and unwanted failures observed during the quasi-static and fatigue tensile loading of structural adhesives. Simple finite element models were also developed to support the arguments drawn from the experimental investigations. Particular parameters causing tab and asymmetrical failures in the bulk of dog-bone adhesive specimens were investigated. Artificial defects at the tab-adhesive interface, causing stress concentrations, intentionally misaligned tabs creating bending moments, different tab manufacturing, different fatigue loading frequency, and different grip pressure, were all considered in this analysis. In addition to the traditional instrumentation, a highspeed camera was also implemented to assist the observations. Experimental results showed that the tab failure occurrence is linked to the grip pressure, which shall be minimized. Other parameters such as grip alignment, tab taper, and loading frequency proved to also have a sizable effect on tab failure.