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

Safe and efficient joints are key for improving the structural efficiency of composite aircraft. This thesis investigates the potential of a multifunctional bondline, combining structural bonding, disbond arrest features and structural health monitoring for this matter. The central research question is how to achieve a functionally compliant design, which ensures disturbances between these functions do not eliminate the benefits regarding the objective of a safe and efficient joint due to the multifunctionality. The approach is a multifunctional disbond arrest feature, functionally integrating the disbond arrest and a sensor function. Experimental results indicate some major challenges, such as a stiffness conflict for the integrated functions, but securing an epoxy bondline without disturbing its static strength proves successful in the end. In addition, the thesis illustrates some interesting aspects regarding the functional compliance concept. It strongly suggests that temporal aspects, e. g. transient material properties need to be considered.

The author:

Julian Steinmetz is a research associate in the group of Prof. Dr.-Ing. Michael Sinapius at the Institute of Mechanics and Adaptronics since 2016. His focus area is multifunctional structures. In the scope of his doctoral thesis, he deals with the functional compliant aggregation of disbond arrest and health monitoring functions with structural bonding for obtaining a safe and efficient joining technology. Julian Steinmetz obtained his Bachelor's and Master's degree in mechanical engineering from the Technische Universität Braunschweig. He has been a visiting student in the research groups of Professor Jonathan Cooper at the University of Bristol and Professors Tsuyoshi Inoue and Kentaro Takagi at the Nagoya University.