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Development and application of hybrid joining in lightweight integral aircraft structures

Project description

A novel hybrid joining technique enhances the mechanical and chemical properties of joints

Joining the large subcomponents of aircraft can be challenging both in terms of the joining process itself and its long-term impact on the integrity of the aircraft. Refill friction stir spot welding is a promising solid-state joining technique using friction to pre-heat and soften a component after which it is shaped to form a joint. The process can lower weight by eliminating fastening elements such as rivets and can also join dissimilar materials. The EU-funded DAHLIAS project is optimising this promising technique and combining it with application of a sealant with adhesive properties. The sealant will not only protect the joint against corrosion but also reinforce its mechanical performance.


The main objective of the DAHLIAS project is to optimise hybrid joining (Refill Friction Stir Spot Welding, RFSSW, with an adhesive sealant bond) for application in aircraft structures. RFSSW is a solid-state joining technology especially applicable to lightweight alloys in similar and dissimilar configurations. The process has been successfully applied to difficult-to-weld and non-weldable alloys and is considered a potential replacement of mechanical fastening. Overlap joints in aircraft structures require the use of sealants for corrosion protection reasons. Using sealants with an adhesive function would complement the high quality joints produced by RFSSW by not only protecting against corrosion but also contributing to the overall mechanical performance of the structure. To achieve the main goal of this project a work plan consisting of eight work packages has been devised. Two work packages are focused on the RFSSW process development using standard samples with and without adhesive sealant. In parallel the adhesive sealant technology, including surface pre-treatment will be developed. The hybrid joining solution developed in this project will be compared to conventional joining technologies to define its potential. Hybrid joining brings a number of advantages to production and performance of aircraft structures. The change from differential to integral design introduces new challenges in the analysis of mechanical performance. Hence, the damage tolerance behaviour of hybrid joints is also investigated in this project. Quality control methods will be investigated by selecting NDT methods and by process control based on online monitoring of parameters. In the last phase of this project technology demonstrators will be produced to evaluate the capabilities of the proposed technology in actual aircraft structures. The consortium (3 R&D and 2 industrial partners) has the exact fitting, prooven expertise and high excellence. HZG (coordinator) holds key patents.


Net EU contribution
€ 283 225,00
21502 Geesthacht

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Schleswig-Holstein Schleswig-Holstein Herzogtum Lauenburg
Activity type
Research Organisations
Total cost
€ 283 225,00

Participants (4)