The Institut de Soudure group and Arkema, in partnership with Hexcel, Latécoère and Stelia Aerospace (France), have won the JEC Composites Innovation Awards 2020 in the Aerospace category for their innovative ISW (Innovative Solutions for Welding).
This welding solution has been co-developed and patented by the Institut de Soudure group and Arkema, with each partner contributing its expertise in welding processes and high-performance materials respectively.
The use of thermoplastic composites represents a major challenge in the aeronautics sector, and requires a welding technology with excellent mechanical performance at an acceptable economic cost. While ISW is specifically designed for welding high-performance polymers (PEKK) reinforced with carbon fibers, it can also be applied to other types of matrix (from PA to PAEK) and fibers (glass, aramid).
According to the Institut de Soudure group, ISW enables the mechanical performance of the welded assembly to be 85 % better than that of non-welded reference plates, without the presence of foreign bodies in the weld joint after operation.
The solution is characterized by a movable metal insert located at the interface and kinematically linked to the welding head. This susceptor provides indirect heating of the composite, in addition to the induction welding and compaction performed by the welding head. The process is also defined by its optimized interface ply of unreinforced or low-fiber-volume thermoplastic matrix, which can be adapted to suit the needs of the application.
The welding head also generates cooling pressure on the substrate, which ensures compaction of the welded interface. "We measure the melting temperature with a laser pyrometer at the susceptor and control the air-blast cooling system of the welding head to remain below the crystallization temperature, so as to eliminate any risk of decompaction once the pressure is released.explains Jérôme Raynal, Director of Aeronautics and Composites for the Institut de Soudure group.
This innovative head with a movable insert is very compact to allow precise and complex access. ISW has been designed to be fully automated, by mounting the welding head on a 6-axis robotic arm.
A project launched in 2017
The Institut de Soudure group has been developing composite welding processes for over 10 years, with a range of technologies including resistance welding, co-consolidation and induction welding.
For Stelia Aerospace's Arches BOX TP demonstration project, unveiled at the Paris Air Show 2017, the Group was in charge of dynamic induction welding the stiffeners to the skin. To do this, the Group developed specific inductors on behalf of Stelia Aerospace. This project was the starting point for the development of induction welding of structural aeronautical parts.
Based on this development, the Institut de Soudure group and chemist Arkema worked on ISW technology, which overcomes the weak points of conventional induction welding.
Since early 2019, feasibility studies have been initiated with key aerospace players such as Stelia Aerospace and Latécoère to evaluate the ISW solution. In 2020, the main objectives are to increase the maturity of the technology and engage in specific projects to go all the way to ISW qualification.
ISW key benefits :
- Mechanical performance of welded assembly (85 % better than reference material)
- Reduced post-operations (no adhesives or chemicals)
- Weight reduction
- No susceptor left in the weld seam at the end of the operation
- Dynamic, controlled and monitored, fully automatic solution
- Ecological impact: use of recyclable materials and low energy consumption
- Suitable for all types of matrix and fibers.