An oxide ceramic matrix composite for high-temperature applications in aerospace and energy
Tubular components made from the oxide ceramic matrix composite WHIPOX®
Gas turbine engines are economically and ecologically highly important for future air transportation as well as power generation. Therefore, the development of green and energy-efficient gas-turbines is a principal research area at DLR. A way to achieve these goals is the development and application of new materials, for example combustion chambers made of high-temperature stable fiber-reinforced oxide ceramics, commonly known also as oxide ceramic matrix composites (CMC). Such CMC liners promise increasing combustion temperatures along with decreasing demand for air cooling. This new approach applies to aero-engines as well as land-based gas-turbines. But also for applications in space transportation and hypersonic flight lightweight oxide CMC materials and structures are being developed and tested. The main advantage of oxide CMC is their excellent transmittance for electro-magnetic waves enabling the fabrication of thermal protection systems which are transparent for RADAR or radio signals used for transmission of telemetry data.
Development and Manufacturing of WHIPOX™
The basic manufacturing step is designing the WHIPOX body and the respective optimized filament winding pattern. Winding patterns are generated by state-of-the-art CAD software and are transferred to the CNC module of the filament winding facility. During filament winding fiber tows are infiltrated with a liquid dispersion of matrix particles and subsequently wound up on a rotating mandrel. Wound bodies are dried and sintered to a rigid CMC at high temperature. Alternatively as-wound bodies can be cut-off the mandrel before drying and be re-shaped; for example to CMC sheet. Typical thickness ranges from less than 0.5mm up to more than 5 mm. CMC components with higher wall-thickness or more complex shape are manufactured by lamination techniques. Upon consolidation WHPOX components can easily be machined by standard methods such as cutting, drilling or milling. Beyond employed ceramic fibers and winding pattern design the development of ceramic matrices is a key for achieving optimized CMC properties and performance. We employ high-end facilities for synthesis, preparation, and characterization of ceramic matrix materials. The development of WHIPOX materials and small components is performed on a custom designed and built winding facility. Since 2103 we run an industrial-scale filament winding facility allowing the fabrication of large CMC bodies having diameters of up to 1000 mm and lengths of up to 3000 mm
Potential applications of WHIPOX™ beyond aerospace and energy
Due to an excellent resistance against thermal cycling and low heat capacity WHIPOX components are ideally suited for industrial thermal processing, e.g. for kiln furniture or burner nozzles experiencing very fast heating and cooling rates. The transparency for EM waves enables induction heating and manipulation in metallurgical melt processing. Moreover, WHIPOX is a non-brittle electrically insulating material which can be operated at temperatures far beyond 1000°C. The highly variable permeability of WHIPOX is attractive for high-temperature and corrosion resistant filter media to be used in solar-thermal or thermos-chemical processes. Generally, for many applications WHIPOX CMC are considered to be smart substitutes for traditional engineering ceramics such as monolithic corundum.