Strength of adhesive joints under impact stress conditions

The paper reports an experimental study on the bonded joints, carried out by means of an instrumented impact pendulum, equipped to load overlap specimens in tensile shear. Such testing configuration is the most adequate and natural to study the possible modifications of the behavior of the joint, changing from static to dynamic loading condition, keeping the same specimen type. The specimens were steel strips bonded by an epoxy adhesive (Hysol 3425). Several values of lap length, adhesive and adherends thickness were adopted, to achieve rupture under different stress combinations. The stress state at rupture has been calculated by means of a structural solution. The results show that it is possible to represent the failure condition on a chart having as axes the peel and shear structural stress, in a way similar to that found for static cases. Furthermore, in spite of the concerns associated with the impact condition, the strength of the adhesive does not decrease with respect to the case of static loading.