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

通过高效轻质材料，特别是CFRP，飞机结构重量的改善在空中客车A350项目中达到了最大程度。全金属机身被合适的CFRP结构所取代，使得纤维增强复合材料的数量超过了整个飞机的50%。通过材料替代的结构轻量化设计似乎已经实现，并且具有高度可变几何形状的CFRP部件的制造工艺仍然是手工工作并且昂贵。因此，在当今的工艺技术下，采用更大批量和更小航程的飞机项目将不会有利可图。当前和未来的方法越来越多地基于在正确的位置使用正确的材料的混合结构概念，因此多材料组件的连接是关键方面之一。混合结构必须满足所有要求的功能，而不会使单个部件尺寸过大。因此，待连接的材料的界面决定了整个混合结构的可实现重量。该研究项目的目标是证明选定的航空航天材料的稳定连接过程。超声波金属焊接是一种非常有前途的焊接技术，在这里，特别是超声波扭转焊接的变体。通过统计试验方法和中心工艺参数的在线测量实现了混合连接。关于特定的航空要求，轻合金/CFRP接头的机械性能通过机械性能方面的特定工艺步骤来表征和修改。为了确保不老化的混合复合材料，所谓的3层混合材料（铝/钛箔/碳纤维增强塑料，铝/玻璃纤维织物/碳纤维增强塑料）将开发和详细研究其微观结构，机械和老化性能。此外，未来的航空航天应用超声波焊接在组件级将检查的混合演示器的设计和制造相应的实现定义的技术准备水平（TRL）。此外，超声波焊接的工业实施的概念将开发使用的一个特定的飞机结构的示范的基础上的例子。

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.