In 2021, Daher delivered thermoplastic composite wing ribs to Airbus UK in the context of the Airbus Wing of Tomorrow programme. Elementary parts of the ribs were assembled with fasteners and Daher realised this solution could be improved. Daher consequently launched a new rib project (Welded Rib) based on infrared welding assembly and innovative design and processes. This programme aimed at enabling lighter aircraft, faster production rates and lower CO? emissions for future single-aisle programmes.

For this project, Daher worked with several partners: AniForm Engineering B.V. from the Netherlands, the Cetim from France, the Luxembourg Institute of Science and Technology and Victrex PLC from UK.

JEC Composites: How does this thermoplastic wing rib project fit into Daher’s long-term strategy as an aerostructures manufacturer in the face of decarbonisation and the ramp-up in production rates for future aircraft programs?

What are the key advances in design, processes and assembly that set this welded thermoplastic rib apart from the aluminium or thermoset solutions currently in use?

Martin Denize: Daher expects to be a strong OEMs partner for future single aisle aircrafts around wing, empennage, movable and fuselage elementary parts. At the end of 2020, Daher successfully delivered wing ribs and spars to Airbus UK as part of the Wing of Tomorrow programme. To further enhance cost and weight reduction in CFRTP composite, Daher launched the Welded Rib project.

Daher’s main strategy was to align the rib development programme with CS-25 certification requirements. Our objective was to develop a new rib design capable of withstanding high mechanical loads while remaining both weight and cost competitive compared to current aluminium solutions. To achieve this, Daher designed and sized two reference ribs with equivalent mechanical performances, one made of aluminium and one CFRTP composite with a mechanically fastened assembly, to serve as benchmarks for weight and cost throughout the entire project. Use of CFRTP composite material for wing ribs enables significant weight reduction compared to aluminium, which results in lower fuel consumption for the aircraft (22% weight saving). Welding of CFRTP composite components allows for additional weight and cost efficiency as it represents an alternative to mechanically fastened assembly method (13% weight saving). Lightweighting of a wing rib results not only from the low density of composite materials but also from rib design optimisation. Indeed, a welded assembly requires less composite material on the elementary parts since specific pitches and space are not required compared to assembly with fasteners (it explains the innovative “wave shape” of the corner part of the rib).

As a result, Daher estimates a reduction of 12,5 tonnes of CO2  for one CFRTP rib compared to aluminium ribs over the lifespan of a single aisle aircraft (which is significant considering all the ribs in wings and empennage structures).

CFRTP composites also offer the opportunity to employ efficient, fast and automated manufacturing processes such as Automated Fibre Placement (AFP), Direct Stamping® and Infrared Welding. These innovative technologies require less energy and significantly reduce production time – by about a quarter – compared to traditional composite manufacturing methods (such as oven or autoclave consolidation, assembly using bolts or rivets). Moreover, they help lower both manufacturing costs and environmental impact by generating less material waste and by minimising the need for auxiliary materials (eliminating vacuum bag setups and sealants near the welded area).

How could this solution transform aircraft wing architectures, particularly in terms of recyclability, assembly costs and large-scale industrialisation?

Our CFRTP rib contributes to innovative wing architecture and facilitate wing assembly thanks to simple design. Daher’s ability to produce very thick-walled parts could also help optimise the quantities of wing components.

Besides, the use of infrared welding reduces assembly cost of 15% compared to mechanically fastened assembly method. Daher is also working on a future production plant digital twin capable of producing thick and large TP parts for single-aisle aircraft.

Daher also sees an opportunity in using TP materials for its recyclability to answer decarbonisation objectives. We have already demonstrated that recycled TP composite parts can be qualified for aerospace applications by replacing aluminium rudder pedals of its TBM aircraft into upgraded Carbon/PPS compound. This Carbon/PPS compound is generated after processing the current continuous fibre composite production waste coming from Daher stamped part production. This technology is intended to be used tomorrow to enhance the end?of?life management of our TP parts. Next step for Daher is to combine recyclability and process versatility of TP composite to propose zero waste solutions.