Recently, European researchers have successfully laser welded an 8-meter-long weld of a carbon fiber reinforced fuselage, showing that it will be possible to manufacture ultra-light passenger aircraft using this method. The demonstration was led by Airbus and participated in by several Fraunhofer institutes. It is said that this research provides a proof of concept for the use of CO2 lasers to join carbon fiber-reinforced thermoplastic (CFRTP) component structures without chips.

1 Dynamic beam shaping

The team at the Fraunhofer Institute for Materials and Beam Technology (IWS) in Dresden, Germany, worked under the "Multifunctional Fuselage Demonstrator" (MFFD) project (part of the EU's "Clean Sky 2" research program). They said that this novel construction method and process can greatly reduce the weight of the fuselage, reduce material consumption, and reduce manufacturing time.

They used a CO2 laser source to weld long welds of large-volume thermoplastic aircraft fiber composite structures outside the autoclave, which is considered a world-first achievement. Maurice Langer, head of the research team, said: On the left side of the MFFD, the process developed by IWS completes the final longitudinal seam welding between the upper and lower halves of an 8m x 4m aircraft fuselage section made of carbon fiber reinforced thermoplastic.

The CONTIjoin process combines CO2 laser technology and high dynamic beam shaping technology to enable real-time control of the laser power to keep the temperature in the joint area constant. At the same time, the process also automatically adjusts the beam shape in the weld gap.

2 Laser wavelength is crucial

The Dresden research team will report its research results at the 2024 International Aerospace Exhibition (ILA 2024). They also said that the 10.6µm CO2 laser wavelength plays a crucial role because the optical absorption rate of 10.6µm CO2 lasers is much higher than that of 1µm fiber lasers currently widely used in industrial welding.

The use of lasers means that the mechanical connection elements and material doubling of traditional riveted overlap joints are not required, so the weight of the fuselage shell made of thermoplastic composites is significantly lower than that of traditional sections. The IWS team points out that this marks an important step in the manufacture of aircraft using new thermoplastic high-performance materials, as it enables the production of high-strength and weldable large components.

3 Overlapping connection

Rauscher said: This opens up the possibility of real-time monitoring and adaptive control of the welding process, which is not possible with conventional control electronics. For example, in addition to controlling the welding temperature along the welding gap, the position, width, and curvature of the aircraft half-shell must also be taken into account.

In the future, the research team's plans will focus on increasing the technical readiness level of the method to obtain qualification certification in the aviation industry and other industries. Langer pointed out: The developed CONTIjoin technology is attractive for aircraft manufacturing and other industries. In addition to the aviation industry, the solution has application value in shipbuilding, truck and trailer manufacturing, rail transport or modern wind turbines.