CT-based traceable interface area detection in Al7075-T6 adhesive bonded structures

In emerging technologies such as aerospace and aeronautics the joining of multi-material parts is a growing need for the development of components with improved properties. Among efficient joining technologies, adhesive bonding is considered an optimal method for joining multi-material structures, however, its use is limited due to inadequate evaluation of bond quality by non-destructive testing (NDT) methods. Recently, computed tomography (CT) is becoming more and more accepted in the non-destructive testing (NDT) community, thanks to the equipment and software development. This technology is capable of performing quantitative dimensional and geometric analysis, for example of adhesive bonds. Nevertheless, quantitative results obtained by CT are strongly influenced by a large number of error sources and thus the accuracy of CT-based measurements remains yet largely uncertain. In most cases a consistent methodology is needed, so that CT could be considered a reliable technology. This paper aims to evaluate the adhesive bonding quality in metal bonded structures by means of CT. To do so, a structural adhesives with four different Aluminum specimens are analyzed. The adhesives used are MERBENIT SF50® and BETAMATE 2810® and the substrates of Al7075-T6 of 3mm thickness. For each bonding configuration, a novel ML-based method for the detection of the contact area between adhesive and substrate is provided. Each adhesive interface area measurement is associated with its corresponding task-specific uncertainty estimation. Results are promising and useful for adhesive bond quality evaluations in CT equipment.