Felix Vogel’s research while affiliated with German Aerospace Center (DLR) and other places

Increasing the efficiency of jet engines is essential to meet the demanded climate targets. Ceramic matrix composites (CMC) are strong candidates for aircraft applications because they withstand high temperatures, while their density is two-thirds lower than that of conventional nickel-based alloys. This leads to cooling air savings and a lower overall engine weight, resulting in a potential reduction of emissions. To investigate the potential benefits and manufacturing techniques required for the introduction of CMC to the high-pressure turbine of a modern jet engine, the geometry of a nozzle guide vane of an existing turbine was redesigned considering ceramic specific constraints. Then, the liquid silicon infiltration (LSI) process was used to manufacture SiC/SiC nozzle guide vanes. Hi-Nicalon S woven fabric was used together with a CVI-based fiber coating. The outer surface of the vane was ground to meet the requirements for surface roughness, and geometric and positional tolerances. Cylindrical, laser-drilled cooling holes were introduced for trailing edge cooling. In the final step, an environmental barrier coating system (EBC) consisting of yttrium disilicate and yttrium monosilicate layers was applied using PVD processing. Wind tunnel testing under TRL 4 will be performed and vane performance will be evaluated.

Increasing the efficiency of jet engines is essential to meet the demanded climate targets. Ceramic matrix composites (CMC) are strong candidates for aircraft applications because they withstand high temperatures, while their density is two-thirds lower than that of conventional nickel-based alloys. This leads to cooling air savings and a lower overall engine weight, resulting in a potential reduction of emissions. To investigate the potential benefits and manufacturing techniques required for the introduction of CMC to the high-pressure turbine of a modern jet engine, the geometry of a nozzle guide vane of an existing turbine was redesigned considering ceramic specific constraints. Then, the liquid silicon infiltration (LSI) process was used to manufacture SiC/SiC nozzle guide vanes. Hi-Nicalon S woven fabric was used together with a CVI-based fiber coating. The outer surface of the vane was ground to meet the requirements for surface roughness, and geometric and positional tolerances. Cylindrical, laser-drilled cooling holes were introduced for trailing edge cooling. In the final step, an environmental barrier coating system (EBC) consisting of yttrium disilicate and yttrium monosilicate layers was applied using PVD processing. Wind tunnel testing under TRL 4 will be performed and vane performance will be evaluated.

Ceramic matrix composites (CMCs) are considered as the most promising materials to replace super alloys in common rocket propulsion systems due to their excellent mechanical and thermal properties at high temperatures and low material densities. To demonstrate the capabilities of CMCs, a test campaign for new upper stage propulsion systems were performed at the DLR Institute of Space Propulsion in Lampoldshausen including a novel uncooled C/C-SiC nozzle extension. The green body was produced by wet filament winding. Following the preform was ceramized to the C/C-SiC state via liquid silicon infiltration. Since delaminations are a major concern of wound CMCs structures, the multi angle fiber architecture, which was used here, mitigates this risk. Computer tomography scans, which were carried out at all stages of the processing, show the changes of the component through each step. Furthermore, the quality of the material formed was determined by microstructure analysis using SEM. The structural integrity and thermal stability were tested by hot gas firing tests under laminar and separated flow conditions. The test proved that the ceramic nozzle shows the advantages of the high mass specific characteristic values and a sufficient high temperature resistance under extreme conditions.

The paper presents manufacture of C/C‐SiC composite materials by wet filament winding of C fibers with a water‐based phenolic resin with subsequent curing via autoclave as well as pyrolysis and liquid silicon infiltration (LSI). Almost dense C/C‐SiC composite materials with different winding angles ranging from ±15° to ±75° could be obtained with porosities lower than 3% and densities in the range of 2 g/cm³. Thermomechanical characterization via tensile testing at room temperature and at 1300°C revealed higher tensile strength at elevated temperature than at room temperature. Thus, C/C‐SiC material obtained by wet filament winding and LSI‐processing has excellent high‐temperature strength for high‐temperature applications. Crack patterns during pyrolysis, microstructure after siliconization, and tensile strength strongly depend on the fiber/matrix interface strength and winding angle. Moreover, calculation tools for composites, such as classical laminate and inverse laminate theory, can be applied for structural evaluation and prediction of mechanical performance of C/C‐SiC structures.

Alternative energy and the transition away from fossil fuels is one of the core subjects of current politics. In the automotive industry the internal combustion engine, however, remains the most commonly used power unit. In terms of improving its environmental compatibility, the current research goal is to increase its efficiency and service life while maintaining or even reducing the fuel consumption. The DLR develops a ceramic fiber-reinforced piston ring, which should contribute to fuel savings and reduced piston wear. In order to investigate fundamental questions of feasibility and functionality, piston ring prototypes made of C/C-SiC (carbon fiber reinforced silicon carbide) were developed in cooperation with the DLR Institute of Structures and Design and DLR Institute of Vehicle Concepts. For a ceramic piston ring the mounting is one of the most restricting requirements, as the material is usually not flexible and fiber reinforcement has to be carefully adjusted in order to provide elastic behavior. Within the project, variants of C/C-SiC with different preforming technology were developed. Weaving-, winding- and tailored fiber placement-technologies were used for preform manufacturing. The mechanical examination of the samples was carried out according to ASTM C1323 - 16 for ceramic C-rings and the results were promising. In addition, the work provides further insights into the expected running behavior of the ceramic piston rings and how economic production can be achieved. Further research now aims at examining the effects on the energy consumption and service life when utilized in IC-engines.

Silicon carbide fiber-reinforced silicon carbide matrix composites (SiC/SiC CMCs) are promising candidates for hot gas components in jet engines. Three common manufacturing routes are chemical vapor infiltration, reactive melt infiltration (RMI) and polymer infiltration and pyrolysis (PIP). A combination of the processes seems attractive: the remaining porosity after PIP process can be closed by subsequent siliconization, resulting in a dense material. This work describes a new approach of a combined PIP and RMI process. SiC/SiC CMCs were manufactured by PIP process using Hi-Nicalon Type S fibers. An additional RMI was carried out after a reduced number of PIP cycles. Microstructure was examined via μCT, SEM and EDS. Bending strength was determined to 433 MPa; strain to failure was 0.60 %. The overall processing time was reduced by 55 % compared to standard PIP route. The hybrid material contained 70 % less unreacted carbon than material produced by LSI process alone.

Silicon carbide fiber-reinforced silicon carbide matrix composites (SiC/SiC CMCs) are promising candidates for components in the hot gas section of jet engines, as they exhibit high temperature resistance and low density compared to their metal alloy counterparts. Three common manufacturing routes are chemical vapor infiltration, reactive melt infiltration (RMI) and polymer infiltration and pyrolysis (PIP). This work describes a new approach of a combined PIP and RMI process. A combination of the processes seems attractive: the remaining porosity after PIP process can be closed by subsequent siliconization, resulting in a dense material. SiC/SiC CMCs were manufactured by PIP process using Hi-Nicalon Type S fibers. Generally, the processing of SiC/SiC, produced solely by PIP route, is rather time-consuming and the composites show a certain residual porosity. In order to obtain a dense matrix and to reduce the processing time, an additional RMI with silicon alloy is carried out after a reduced number of PIP cycles. To protect the fibers during the siliconization, a CVD fiber coating was applied. Microstructure was examined via microCT, SEM and EDS. Bending strength was determined to 433 MPa; strain to failure was 0.60%. The overall processing time was reduced by 55% compared to standard PIP route. The hybrid material contained 70% less unreacted carbon than material produced by LSI process alone.