Abstract
Ongoing research in the area of adhesive bonding is focused on the optimization of the bonding method used as well as on the use of newly developed high quality adhesives. In this work, the bonding quality of adhesively bonded composite U-joints was experimentally investigated using C-Scan ultrasonic inspection. The reference adhesive used was Epibond, while the newly developed adhesive was the one developed within the ABITAS project. Based on the geometry of the U-joint, different scan areas of the two existing bondlines were defined in order to effectively capture the quality of the entire bonded area. Furthermore, two different bonding methods were evaluated in terms of bonding quality assessed through the ultrasonic inspection tests. In this frame, U-joints including normal cured and spot cured bonded areas have been investigated. The evaluation was carried out on the basis of the total defected area by using the clustering mode of ULTRAWIN image analysis software. This mode enables the quantitative assessment of the defective percentage (%) out of the total scanned area. The results reveal a significant amount of voids in the components investigated. In most cases, spot curing areas are clearly distinguishable. The spot curing process causes a variation of the adhesive layer thickness and the creation of bubbles. Comparison between the conventional and the newly developed adhesive was made; for components using the conventional adhesive, damage is located mostly around the rivets, probably due to the increased local pressure.
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