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Three different oxide/oxide ceramic matrix composite (CMC) materials are described. Design concepts for the attachment of the CMC component to the metal structure of the gas turbine are developed in a first work stream focused on the combustion chamber and the turbine seal segment. Issues like environmental barrier coating (EBC)/thermal barrier coatings (TBC), application and volatilization, allowance for the different thermal expansion and the mechanical fixation are addressed. The design work is accompanied by CFD and FEM simulations. A variation of the microstructural design of the three oxide/oxide CMC materials in terms of different fiber architecture and processing of matrix are considered. Also, mechanical properties of these variations are evaluated. The material concepts are developed further in a second work stream. The CMCs are tested in various loading modes (tension, compression, shear, off-axis loading) from room temperature to maximum application temperature focusing on tensile creep behavior. By modification of the matrix and the fiber-matrix interface as well as EBC coatings, the high temperature stability and the insulation performance are enhanced. An outline of the “High Performance Oxide Ceramic”-program HiPOC for the following years is given, including manufacturing of a high-pressure tubular combustor and turbine seal segments from the improved materials as technology samples, for which validation testing up to technology readiness level 4 is scheduled for 2011.

In the present study, we elucidate the influence of oxidative heat exposures at 1000 and 1200°C on an alumina fiber-reinforced polymer-derived ceramic matrix composite containing small residual amounts of carbon. Therefore, we investigated the flexural performance and fracture toughness of on-(0°/90°) and off-axis (45°) reinforced samples. Acoustic emission was used to monitor the internal damage and its progression during loading. At 1000°C, a moderate reduction of strength and fracture toughness is found while after exposure to 1200°C a dramatic decrease down to 50 % is observed. For all composites, a reduction of the damaged volume was found after heat treatments indicating a decrease of crack deflection. However, especially at 1000°C, composites reinforced in 0°/90°direction seemed to be more affected, as no detrimental effect on the mechanical performance was found for the 45°composites. Remarkably, the oxidation-induced silica formation increases the absolute and relative damage thresholds of all composites. A Griffithlike linear relationship between strength and toughness is found. These findings are pivotal for designing and engineering next generation CMCs toward long-term applications.