Aerospace

Additive manufacturing (AM) is considered a key technology for the production of lightweight components and structures. Among AM processes, Laser Material Deposition (LMD) stands out as it can be used to manufacture a wide variety of free-form surfaces. For this reason, LMD can be flexibly applied to repair and coat as well as to selectively individualize and functionalize prefabricated basic components (hybrid additive manufacturing).

However, the processing of aluminum alloys with laser-based methods is challenging, especially because these alloys have a low degree of absorption and high thermal conductivity. This means that adapting the LMD process control to the specific material plays a decisive role in opening up lightweight construction applications with aluminum materials.

Powder-based LMD was used to process aluminum alloys with silicon, magnesium and zinc – as the main alloying elements – in order to produce structural elements such as tracks, layers and solid bodies. Scientists of Fraunhofer ILT are investigating process regimes that span orders of magnitude in terms of key process parameters, such as feed rate and deposition rate. Since the process control has been fundamentally advanced, new types of lightweight construction applications with aluminum can be put into practice, e.g. in the aerospace, automotive and mechanical engineering sectors.

Fraunhofer ILT is developing and building the Laser Optical Bench as the core element of a laser beam source for the German-French climate mission MERLIN (Methane Remote Sensing LIDAR Mission). This bench constitutes the laser transmitter along with the pressure housing developed by Airbus and the cooling, supply and control units. The aim of the mission is to measure the greenhouse gas methane in the Earth's atmosphere from a satellite. The laser pulses backscattered from the Earth's surface will provide information about the methane concentration of the overlying atmospheric column.

The complex and compact laser system must be insensitive to strong vibration and temperature fluctuations. Since the enclosed system must have a service life of more than three years, it is necessary to do without outgassing materials to avoid contamination.

In addition to the optical elements, the design includes a passive cooling structure and an electrical harness for signal, high-current and high-voltage transmission for laser operation. Soldering techniques are used to contact electrical components and to mount the optics, ensuring robust, ultra-precise and contamination-free connections for a long service life. The institute has demonstrated that the system is able to resist environmental loads and that it performs as required. After the successful completion of the Critical Design Review, the client Airbus Defence and Space GmbH and DLR Space Management confirmed and approved the design.

The work is being funded by the BMWi (German Federal Ministry for Economic Affairs and Energy) under the reference number 50EP1601 and is being carried out on behalf of DLR Space Management by Airbus Defence and Space GmbH as a subcontractor.