Design, Manufacture and Quality Assurance of C/C-SiC Composites for Aeronautics and Space Transportation Systems

Kurzfassung

Ceramic Matrix Composites, manufactured via the Liquid Silicon Infiltration (LSI) process, show a wide variability of microstructures, thermal and mechanical properties. Depending on the fiber preform and the processing conditions, these C/C-SiC composites can be tailored to specific applications. Generally, the high amounts of carbon fibers limit their use with unprotected surfaces under oxidative atmospheres to some few hours. External coatings, for example those based on CVD-SiC, RB-SiC or yttrium silicate, improve the oxidation as well as abrasion resistance of C/C-SiC considerably. Nevertheless, carbon-based CMCs are preferred materials for limited lifetime structures, i.e. a certain degree of ablation and erosion has to be accepted. As a consequence, non destructive evaluation tests are obligatory to survey the respective state of the material. Moreover, new and adapted NDE-methods have been investigated to assure the quality of the composite during the three-step LSI-process. For example, using novel air-coupled ultrasonics, it is possible to examine the CMC product at every manufacture step, including the highly porous carbon-carbon phase. This permits an almost complete analysis of the whole LSI process and enables an early detection of faults. Another novel approach for quality assurance are thermographic methods, which allow a fast global damage assessment by analyzing the heat transfer into the component. Both, the thermographic analysis and air-coupled ultrasonics, are non-contact methods for damage assessment and can be used in any stage of production. Additionally, a current technology project of DLR’s space research will be described. An experimental TPS structure which is planned to be launched with a Russian FOTON capsule, has been designed and manufactured to evaluate different coating materials under reentry conditions. Chemical vapor deposited SiC, low pressure plasma sprayed yttrium silicate and titanium dioxide coatings were applied on the surface of a C/C-SiC panel of 300 mm diameter. The paper deals with different aspects of the design, manufacture and quality assurance of C/C-SiC composites with respect to their use in jet vanes of rocket motors and for thermal protection systems.