Joining of light alloys to fiber reinforced composites for hybrid lightweight applications in aircrafts by high power ultrasonics

• Applicant: Professor Dr.-Ing. Frank Balle
• Subject Area: Polymeric and Biogenic Materials and Derived Composites ; Mechanical Properties of Metallic Materials and their Microstructural Origins
• Term: from 2015 to 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 263047333

The improvement of the structural weight of aircrafts by efficient lightweight materials, especially CFRP, has reached a maximum with the Airbus A350 project. The substitution of full-metal fuselage by a suitable CFRP structures has driven the amount of fiber-reinforced composites to over 50%, regarding the entire aircraft. Structural lightweight design by material substitution seems to be achieved and manufacturing processes for CFRP components with high variable geometries are still manual work and expensive. So following aircraft programs with higher volumes and smaller ranges will therefore not be profitable with today's process technology. Current and future approaches are increasingly based on hybrid structures following the right material at the right place-concept and joining of multi-material components is consequently one of the key aspects. A hybrid structure must satisfy all required functions without oversizing the single components. As a result the interface of the materials to be joined determines the achievable weight of the entire hybrid structure. Objectives of the research project are the evidence of a stable joining process for selected aerospace materials. As a highly promising technique ultrasonic metal welding was selected and here especially the variant of ultrasonic torsion welding. The hybrid joints are realized by statistical test methods and online measurement of the central process parameters. Regarding specific aviation requirements, the mechanical properties of light alloy/CFRP-joints are characterized and modified by specific process steps in terms of mechanical performance. To ensure non-ageing hybrid composites so called 3-layer hybrids (Al/Ti-foil/CFRP, Al/GF-fabric/CFRP) will be developed and investigated in detail regarding their microstructural, mechanical and aging properties. Furthermore a future aerospace application of ultrasonic welding at component level will be examined by the design and manufacturing of a hybrid demonstrator corresponding to the achievement of a defined Technology Readiness Level (TRL). In addition, a concept for the industrial implementation of ultrasonic welding will be developed using the example of a specific aircraft structure based on the demonstrator.

• DFG Programme: Research Grants (Transfer Project)
• Participating Institution: CTC GmbH Stade