Further information:

Ralf Engelhardt, M.Sc., Technische Universität München/Technical University of Munich,
Lehrstuhl für Carbon Composites (LCC)/Chair of Carbon Composites, Garching bei München,
engelhardt@lcc.mw.tum.de, www.lcc.mw.tum.de


16. March 2018

Thermoplastic CFRP-Module for a Sounding Rocket with Integrated Fiber Optic Sensors is ready for Liftoff

The Chair of Carbon Composites (LCC) at Technical University of Munich (TUM) developed and implemented a manufacturing concept for a carbon fiber reinforced module of a sounding rocket in cooperation with the German Aerospace Center (DLR). The CFRP-Module was qualified for flight as part of a REXUS rocket mission and is now ready for the launch in March 2018.

Reducing the structural weight of a rocket allows higher payloads, higher apogees or reduced fuel consumption. DLR operates sounding rockets to perform experiments during its sub-orbital flight. The modular structures of these rockets are typically made out of aluminum. To increase the performance of the rockets TUM developed and implemented a manufacturing concept for a thermoplastic CFRP-module with integrated fiber optic sensors as part of a project funded by the Federal Ministry for Economic Affairs and Energy.

CFRP-module set-up

A module consists of a thin cylindrical shell with bulky load input rings on both ends as bolting interface to the neighboring modules. The manufacturing was split into separate steps for the load input rings and the cylindrical shell. The rings were manufactured by pressforming of long fiber reinforced thermoplastic granules (LFT). Thermoplastic Automated Fiber Placement (TP-AFP) was used for the manufacturing of the shell structure. The closed loop control of the TP-AFP process parameters allows an insitu consolidation of tapes on the substrate and on the previously manufactured load input rings. This way there is no need for a subsequent consolidation in an autoclave.
Polyetheretherketone (PEEK) was used as matrix polymer due to the high mechanical and thermal loads.

Manufacturing data

The LFT- and tape-materials were characterized on coupon level at room temperature and service temperature of 135 °C to generate input values for the structural analysis and dimensioning. Subcomponent tests of the in situ bond between shell and rings as well as screw pullout tests covered critical aspects of the module design. On full-scale level a vibration test and a bending test until failure were performed with the dedicated test hardware module. For the
flight a separate flight hardware was built.
Capsuled fiber Bragg grating (FBG) sensors were integrated in the TP-AFP laminate during manufacturing at different positions. A measurement system was installed inside the module to operate the sensors and handle the data. This will allow temperature measurements within the laminate during flight.

Duty in space

The CFRP-module with integrated sensors and measurement system is part of REXUS mission XXIII with a scheduled launch window mid-March in Kiruna, Sweden. The REXUS program gives universities all over Europe the opportunity to perform experiments on sounding rockets. It is realized as a bilateral agreement between DLR and the Swedish National Space Board. Further information on the mission as well as livestreams of the launch and measurement data are available on the LCC website.