Typical fuselage section in thermoplastic design, out of autoclave skin manufacturing, stringer and frame integration via resistance welding
DLR (CC BY-NC-ND 3.0).
Double curved fuselage section, manufactured by laser assisted tape placement
Flawless laminates with a thickness of 11 mm manufactured by out-of autoclave technology
Stringer-stiffened skin, manufactured with VCT technology and co-consolidated stiffener elements, dimension of 1000x600 mm
Three resistance welded profiles for pull tests
CC BY-NC-ND 3.0.
Welded profile with tensile load - picture taken in the moment of failure. Crack initiation simultaneously in L-profile and laminate top layer
200x magnified microscope image of a resistance welded joint zone. In the center, the carbon fabric conductor can be seen, which is surrounded by electrically insulating glass fabrics. The individual layers of the joined laminates can be seen at the top and bottom of the picture.
Technology demonstrator as part of a typical fuselage section in a thermoplastic design. The demonstrator consists of a skin, stiffened by three stringers, a frame segment and three cleats. The stringer stiffened skin is manufactured in an out-of-autoclave co-consolidation process, while the frame and the cleats are integrated by resistance welding.
As part of the TB-Rumpf project, the autoclave-free consolidation of thermoplastic laminates and resistance welding are being further developed and validated as technology bricks for future thermoplastic aircraft fuselages. The work is being carried out in collaboration with partners from the aerospace industry and further research institutes.
State of the art for the consolidation of large-area components made of continuous fiber-reinforced high-temperature thermoplastic, such as CF-PAEK, is autoclave consolidation. Through an optimized process setup and tailored process control, it is possible to achieve complete consolidation using only temperature and vacuum pressure. The use of self-heated molds or ovens can eliminate the need for an autoclave and thus generate cost advantages. TB-Rumpf aims to mature the process called VCT (Vacuum Consolidation Technique) and to determine the process limits in terms of maximum possible laminate thickness.
The weldability of thermoplastic structures represents an essential aspect for the future use of this material group. Resistance welding in particular is characterized by high achievable strengths and is therefore of great importance for thermoplastic fuselage structures. Within the framework of TB-Rumpf, the welding process itself as well as the necessary welding elements are specifically optimized and the achievable mechanical values are validated.
The results presented here were achieved within the TB-Rumpf research project (FKZ: 20W1721D) in the framework of the Federal Aviation Research Programme V-3, funded by the Federal Ministry for Economic Affairs and Energy, on the basis of a decision by the German Bundestag.