The conventional solution for the joining of large-scale aircraft fuselage structures is either riveting, adhesive bonding or a combination of those. This also applies to scenarios where the fuselage is made out of fiber-reinforced polymer composites (FRPs). As thermoplastic matrix poylmers get increasingly more prominent in use, joining approaches based on welding processes open up new possibilities for manufacturing. Developed at Fraunhofer IWS, advanced laser in-situ joining (AL-IN) is a continuous layup technique for carbon fiber-reinforced laminates. While generally being similar to Automated Tape Laying (ATL) or Automated Fiber Placement (AFP), AL-IN makes it possible to process fully consolidated, multidirectional laminates with up to six plies instead of relying on single-layer unidirectionally reinforced composite tapes, while achieving an in-situ co-consolidation without further post-processing. 
This study shows the general principle of AL-IN and the mechanical performance of samples manufactured using it. A carbon dioxide (CO2) laser was used as an energy source, while highly dynamic beam shaping via a galvanometric mirror system ensured homogeneous heat input. A PID control system with a pyrometric temperature sensor regulated the laser output power to maintain high accuracy to the selected set temperature. For applying the consolidation force, a segmented roller system with an elastic sleeve coating was used in combination with pneumatic actuators. 70 mm wide laminate straps were stacked during the joining process to create a sample with 24 plies in total. Interlaminar shear strength (ILSS) samples were extracted and tested, with resulting strengths reaching as high as 87 % of a reference joint made by static heat press co-consolidation. The work presented is part of the Clean Sky 2 campaign to join the half-shells of the full-scale multifunctional fuselage demonstrator (MFFD), the world's largest known aircraft structure made of thermoplastic composites.

Acknowledgments
This project has received funding from the Clean Sky 2 Joint Undertaking (JU) under grant agreement No. 945583. The JU receives support from the European Union’s Horizon 2020 research and innovation programme and the Clean Sky 2 JU members other than the Union.