Functional Compliance of Multifunctional Bondlines with Disbond Arrest and Health Monitoring Features for Safe and Efficient Composite Joints (2024)

Safe and efficient joints are key for improving the structural efficiency of composite aircraft. Therefore, this thesis investigates the potential of multifunctional bondlines, combining structural bonding, disbond arrest features, and structural health monitoring. The central research question is how to achieve a functionally compliant design. This means ensuring disturbances between these functions do not eliminate their benefits regarding the objective of safe and efficient joints. The approach is adding discrete multifunctional disbond arrest features, functionally integrating disbond arrest and sensor functions, to epoxy bondlines. Experimental results indicate some major challenges such as a stiffness conflict for the integrated functions. Nevertheless, securing the epoxy bondline without disturbing its static strength proves successful in the end. In addition, the thesis provides some new insights regarding the functional compliance concept. For example, it strongly suggests considering temporal aspects, such as transient material properties.