Fiona KESSEL, Martin FRIESS, Carolin RAUH, Alexander WAGNER
DOI Number: XXX-YYY-ZZZ
Conference number: HiSST 2024-0066
In the field of hypersonic systems and their missions, the occuring flows impose extreme mechanical and thermal loads on the materials used. At German Aeroscpace Center (DLR), extensive research is conducted in this area, ranging from design and specification to suitable material developments, and concluding with the proof of concept under realistic conditions in wind tunnels. In recent years, ceramic matrix composites (CMCs) have been investigated for specific aspects of hypersonics. These materials exhibit consistent mechanical behaviour over a wide temperature range (up to 1600 °C), coupled with high damage tolerance and thermal shock resistance, distinguishing them from metals and superalloys. Particularly, special porous C/C-SiC ceramics (carbon-fibre-reinforced carbon with silicon carbide) enable innovative material applications for components in transpiration cooling, fuel injection, or ultrasonically absorbtiv surfaces. The work presented here focuses on the next generation of porous C/C-SiC ceramics currently in development. By deliberately modifying the textile preform, the resulting microstructure and pore morphology are influenced, allowing for control over both the total volume and the orientation of the pores. Relevant parameters influencing porosity have been determined based on the results, and an initial characterization has been conducted. It has been demonstrated that there is a preferred direction of porosity within the sample thickness (z-axis), and in terms of hypersonic-relevant properties, a reflection coefficient of 0.7 at 0.1 bar and f=300kHz, as well as a flow resistance of 3.4 MPa s/m², have been shown to be beneficial. Building upon these promising initial findings, the goal is to further expand the understanding of the parameters influencing porosity and to generate a tailored material for different application scenarios by correlating them with hypersonic properties.