Aircraft manufacturers identified some decades ago that the joining of aircraft structural elements with adhesive bonding is a key technology to low weight, high fatigue resistance, robustness and an attractive design for cost structures. The early wooden aircrafts, the De Havilland Mosquito, Fokker 50, Saab 2000 and the new Airbus A380 are milestones, which prove a long tradition of adhesive bonding in the aircraft industry. However, the adhesive bonding of structural elements is still restricted, mainly due to a lack of universal, economic and robust processing techniques. Further technical progress in this area is crucial for increased functional and economic benefit.
Different European aircraft manufacturers (producers of helicopters, civil and military jets) identified that the advancement of adhesive bonding technologies is of great interest to all. Due to the complexity of this challenging issue, collaboration on a European level with support from selected research institutions could be very beneficial.
ABiTAS therefore clearly contributed to both the top-level objectives identified in the Strategic Research Agenda and the Vision 2020 report to meet society’s needs for a more efficient, safer and environmentally friendly air transport and to win global leadership for European aeronautics.
The central target of ABiTAS was the development of a more robust, flexible and economic processing chain for the assembly of structural elements made from polymer composites and titanium by adhesive bonding, in order to boost the feasibility of new structural concepts as they are envisaged by a number of current European and national research and demonstrator projects.
Therefore ABiTAS aimed at the following four major innovations and their integration into one processing chain:
- Reliable, fast and cost-effective pre-treatments for polymer composites and titanium alloys, which assure durable bonding and are applicable for automated processing.
- On-line monitoring of the physico-chemical state of treated polymer composite surfaces for more effective quality control.
- Adhesive chemistry, which enables more flexibility with processing and assembly via bonding on command and the introduction of new material functionalities.
- Combination of advanced fit analysis, automated bond-line gap adapted application and advanced assembly technology, which incorporates techniques for fast fixation and reaction initiation to reduce assembly pressure and to shorten cycle times.
The trans-national consortium of 15 partners was well prepared to achieve the objectives. It covered the full range of competencies required for all relevant topics and was well balanced, due to the involvement of major European aerospace manufacturers, SMEs and RTD groups, including a university from Greece.
The high complexity of the described challenges and the limited timeframe forcee a parallel work flow and required strong interconnection between the partners. Starting with collecting, structuring and assessing the general and specific requirements in Work Package 1, research and basic developmental work was performed in parallel in the field of new adhesive development, automated surface treatment and online sensing of physico-chemical conditions at the surface (Work Packages 2, 3 and 4). The work on surface pre-treatments and surface sensing methods was concerted to form a basis for the development of a closed concept for online monitoring and surface pre-treatment, which was further developed and realised in Work Package 5. The processing technology for the new adhesive formulations was developed in Work Package 6. Finally the prototypes developed within Work Packages 2, 5 and 6 were combined into the envisaged novel processing chain, which underwent a comprehensive and critical assessment in Work Package 7.
The outputs of this project are the consequent advancements of young technologies like:
- automated surface pre-treatment
- a fast laser triangulation-based fit analysis system
- gap-adapted application system and new developments like:
- adhesives, which combine high strength and durability with flexible processability like improved wetting behaviour, multiple curing temperature or a bonding-on-command functionality,
- a monitoring system for sensing the physico-chemical state on polymer composite surfaces in an industrial manufacturing environment.
All these achievements enable the set-up of advanced bonding processing, which allow the integration of processing steps, reduction of heavy, costly manufacturing tooling and a cycle-time decrease in structural assembly.
This will give the European aerospace industry the opportunity to supply less expensive products than their competitors, reduce the direct operating costs.