Production and Characterization of Porous C/C Material

Kurzfassung

In todays rocket combustion chambers extremely high heat loads are apparent. Reducing these loads in combination with a weight reduction of the thrust chambers structural weight can be achieved with transpiration cooling applied to composite carbon/carbon materials (C/C). In the SFB-TRR 40, subproject A5, evaluating this cooling technique is being the set goal. This paper presents the manufacturing process and the material specific characterization. First, the liquid silicon infiltration process (LSI) is being outlined, followed by the description of techniques used for the determination of the open porosity (ε) and the Darcian (Kd) and Forchheimer (Kf ) permeability coefficients of these composites. Last are important design parameters, yielding the pressure drop for a certain coolant mass-flow rate. For the porosity, the archimedes principle was applied. The typical porosity of C/C ranges from ε = 8 % up to ε = 13 %. Kd and Kf were determined by measuring the pressure drop for a set mass-flow rate through a material specimen. From this data, using a least-square fitting technique, the permeability coefficients can be derived. For C/C Kd typically lies in the order of 10−13 and Kf normally in the order of 10−8.