Lifetime assessment of structural adhesive joints by combining effects of mechanical load, humidity, moisture and UV: design of a test rig

This research covers the design of a novel dual-actuator servo-electric test rig for conducting mixed mode fracture testing of adhesively bonded specimens under changing environmental conditions. Typically, fracture testing of such specimens is directly performed on a dual actuator test rig after artificial ageing in a climate chamber. As the cumulated effects of mechanical and environmental loading cannot simply be decoupled, there is a need for combining a climate chamber with a mechanical loading test rig. The resulting rig enables static and dynamic mechanical testing in an ageing environment combining temperature, humidity and UV effects. The test rig will be used to study and validate mixed mode criteria of, amongst others (T)DCB-samples subjected to extreme combined environmental factors. The introduction of this paper extensively discusses documented research on the effects of moisture, temperature and UV radiation on adhesives and adhesive bonds. Based on the specimens to be tested, the requirements of the test rig are defined. In this paper, the necessity for the combined complete test setup, its design and functionalities are described. In order to demonstrate the accuracy of the test rig concerning measured load and displacement, validation tests are presented.