Papers by Keyword: CFC

Abstract: General materials can satisfy the structure strength requirement of space effective payload easily. But it can hardly satisfy the structure stiffness requirement of space payload. Carbon fiber composite has many excellent properties, such as high relative strength, high relative stiffness, small expansion coefficient, good fatigue resistance and excellent vibration resistance. It can be used to make space products. Firstly, this paper discussed the properties of carbon fiber composite material. Compared with common materials, such as aluminum alloy and titanium alloy, carbon fiber composite material is more suitable for applications of space instruments. Secondly, the metal part embedded technique of carbon fiber composite structure was studied. According to the carbon fiber composite structure of a space camera frame, a few structure forms of embedded part ware studied. A space camera frame of carbon fiber composite was designed and manufactured. Finally, finite element analysis and mechanical tests on the space camera frame was carried out. The results reveal that the characteristic frequency of carbon fiber composite frame is up to 104Hz.The space camera frame is of high stiffness and dimensional stability.

Abstract: Thin TiCx films with a range from pure Ti to stoichiometric TiC (0 ≤ x ≤ 1) have been deposited on carbon-based materials by dual magnetron sputter deposition. The wetting behaviour of a Cu Ti alloy on TiCx coatings has been characterized using the sessile drop method. For these experiments a contact angle measurement device was constructed and successfully tested. Both, stoichiometric TiC and Ti coatings improve wetting dramatically. In between there was no significant wetting improving effect compared to the uncoated case. Subsequently, TiCx coated C/Cu braze joints have been tested on their ability to withstand mechanical loads and analysed with respect to their fracture behaviour.

Abstract: In Plasma Facing Components (PFCs) for nuclear fusion reactors, the protective material, carbon based or tungsten, has to be joined to the copper alloy heat sink for optimum heat transfer. High temperature vacuum brazing is a possible joining process as long as a proper interlayer is introduced to mitigate the residual stresses due to the mismatch of thermal expansion coefficient (CTE). Pure copper can act as plastic compliant layer, however for carbon based materials a proper structuring of the joining surface is necessary to meet the thermal fatigue lifetime requirements. In this work pure molybdenum and tungsten/copper Metal Matrix Composites (W-wires in Cu-matrix) interlayers have been studied as alternative to pure copper for carbon based protective materials in flat tile configuration. Finite element simulations of the brazing process have been performed to evaluate the expected residual stress reduction near the metal-carbon interface. In fact it has been demonstrated that stiff low CTE interlayers can shift the peak stresses from the weak carbon-metal interface to the strongest metal-metal one. Relevant samples have been manufactured and subjected to preliminary metallographic and thermal shock tests. Results obtained so far are encouraging and active cooled mock-ups are being prepared for high heat flux testing. Research work is in progress as regards monoblock configuration with both Wf/Cu MMC and graded Cu/W plasma sprayed and HIPped layers.

Abstract: An overview on parameters influencing the oxidation behaviour of carbon based materials in oxidizing gases is presented in order to support the development of advanced carbon containing materials with high oxidation resistance. Facilities for testing the oxidation behaviour, as operated in FZJ, are explained. Results of exemplary oxidation tests in air at 700°C on diverse new developed materials are presented: Ti and Zr dopings and coatings were found less efficient, whereas Si coatings/dopings significantly reduce oxidation rates. Low oxidation rates of 3D-CFCs without doping/coating, which were manufactured under temperature treatment of > 2200°C and used high purity starting materials, point out the relevance of the latter parameters. Future work on oxidation resistance of carbon based materials is shortly discussed.

Abstract: The optimization of CFC/Cu-interfaces for plasma facing divertor components in thermo-nuclear fusion reactors is proposed and demonstrated via an integrative numerical-experimental approach mainly comprising a macro-scale to micro-scale finite element modeling technique together with fracture mechanics tests. Results obtained by finite element analyses of real-scale CFC flat tile divertor components under high heat flux loading conditions are verified by the findings of tests in an ion beam high heat flux facility. From the macro-scale FE models of the full component the loading conditions are derived for micro-scale FE models that incorporate principal details of the micro-structured CFC/Cu-interface thus allowing to capture explicitly locally acting dissipative mechanisms which in turn at the macro-scale in fracture mechanics experiments increase the fracture toughness of the CFC/Cu-interface.