P 955 - Ageing progression in bonded joints under complex loading

In addition, a selection of reference samples was characterised using non-destructive testing methods. AS 2 characterised the temporal-local ageing progress in the polymer network of the adhesives using p-ATR-IR spectroscopy. In AS 3, thick tensile shear specimens were aged under a static load and then mechanically characterised. In addition, non-destructive testing of the aged samples was carried out to detect cracks and delaminations and to determine the viscoelastic material properties of the adhesives. The IR spectroscopic characterisation of the constantly loaded samples was carried out in AS 4. In this way, the temporal-local progress of chemical ageing in samples aged under constant tensile shear stress could be selectively documented. In AS 5, ageing under wedge splitting stress and climatic exposure was investigated. The macroscopically recognisable crack propagation was measured. After the ageing exposures, the wedge splitting samples were opened and the residual force recorded. The IZFP examined the wedge splitting samples in AS 6 using linear ultrasonic methods for macroscopically undetectable cracks and delamination and determined the viscoelastic properties of the adhesives in both the unaged and aged states. Non-linear ultrasound spectroscopy was also used to examine the areas in front of crack tips for incipient damage, i.e. changes in material behaviour. In order to be able to follow the crack progression in situ using non-destructive testing methods, a method was developed that made it possible to observe crack initiation and crack progression during the wedge gap test. In AS 8, the fracture surfaces of the wedge splitting samples from AS 5 and AS 7 were analysed. Since the position of the crack tip was known, it was possible to analyse the local chemical changes using p-ATR-IR spectroscopy. The chemical states of the ageing adhesive on both sides of the crack tip progressing under the influence of the damaging effects were compared at defined ageing times. The dynamics of the crack progression and the influence of the load level in the crack tip on the damage progression were analysed in AS 9. A wedge crack test with controlled load application was designed for this purpose. Research centres 1 and 2 (AWOK and IZFP) planned 30 man-months to work on the project, while the research centre (LAIP) planned 24 man-months. The work carried out was necessary and appropriate.