Two different advanced architecture woven composite materials were investigated in this study. Mechanical static tests were perfomed to evaluate the woven architectures.A micromechanics analysis (WeaveMAT) that discretely models the yarn architecture within the textile repeating unit cell, was used to predict the stiffness and strength properties of the woven composites under various loading conditions. The calculated overall stiffnesses, and strengths correlated well with the test data for both the woven architectures. A parametric study indicated that a small increase in the weaver yarn percentage increases the interlaminar tension and shear strengths significantly. Also, an increase in the through-thickness orientation of the weaver yarns increases interlaminar tension strength significantly but could decrease the interlaminar shear strength. The WeaveMAT code was found to provide a simple and cost effective means of evaluating angleinterlock woven architectures.
Ceramic matrix composite (CMC) turbine vanes, due to their high temperature capability, allow significantly higher firing temperatures with minimal cooling. Turbine vanes were designed for a gas turbine engine with special attention to attachment methods that minimize thermal stresses due to large differences in coefficients of thermal expansion between the CMC airfoil and metal platforms. Detailed aerodynamic, thermal and structural analyses were performed to ensure component reliability. The paper describes the component design, analysis, fabrication, and rig testing of a silicon carbide fiber reinforced silicon carbide matrix (SiC/SiC) turbine vane.
UTRC and P&W Canada partnered to demonstrate an advanced combustor configuration that was enabled by high temperature CMC materials, in a PW200 series combustor. The PW200 series have reverse-flow combustors and the program presented significant challenges in design and fabrication. The advanced CMC configuration was successfully tested in a PW206 combustor rig. At full power, a 40–50% reduction in pattern factor relative to the bill-of-material metal combustor was measured. The combustor exit plane temperatures were generally better mixed due to the combined effects of (1) eliminating the cold film layers near the combustor walls and (2) the increase in fuel injector count enabled by the increase in dilution air. The CMC combustor was also successfully tested in an engine configuration. Post test gas path surfaces of the EBC coated CMC combustor components were in good condition.
Hybrid bearings containing large silicon nitride balls are considered a critical technology for high speed turbine engine bearing applications. High costs of the balls as well as the lack of a reliable life prediction methodology have hindered extensive use of hybrid bearings in aerospace applications. The presence of surface cracks on silicon nitride balls necessitates the development of a fracture mechanics based approach for life prediction. The key element of the fracture mechanics based approach is the identification of a critical flaw size in silicon nitride balls. Finite element analysis was performed to parametrically vary the crack geometry and to determine the worst case crack geometry conditions. Stress intensity factors were computed for the worst case crack under Hertzian contact loading and in the presence of traction stresses. Failure maps were created that provide a prediction of the maximum permissible surface flaw in silicon nitride bearing balls. Single ball rig tests were performed with induced C-cracks to validate the predictions. Results from the single ball rig test were in good agreement with the results of the analysis for spontaneous spallation. The results of the analysis indicate that 100 μm deep cracks should not cause failure under nominal bearing operation conditions.
Ceramic Matrix Composite (CMC) combustor liners, due to their high temperature capability, enable the elimination of film cooling present in current metallic liners without increasing the pressure drop in the combustor section of a gas turbine engine. The absence of film cooling and the higher temperature capability of the CMC liner leads to complete combustion of carbon monoxide (CO) close to the combustor walls, resulting in a lower emissions combustor. The benefit of lower CO emissions was predicted through the use of stirred reactor network models in which a series/parallel set of individual perfectly stirred reactors (PSRs) is coupled to simulate a combustor. The paper describes the component design and analysis, emissions modeling, fabrication, and sector rig testing of silicon carbide fiber reinforced silicon carbide matrix (SiC/SiC) combustor liners.
As interest grows in the use of ceramic matrix composites (CMCs) for critical gas turbine engine components, the effects of the CMCs interaction with the adjoining structure needs to be understood. A series of CMC/material couples were wear tested in a custom elevated temperature test rig and tested as diffusion couples, to identify interactions. Specifically, melt infiltrated silicon carbide/silicon carbide (MI SiC/SiC) CMC was tested in combination with a nickel-based super alloy, Waspaloy, a thermal barrier coating, Yttria Stabilized Zirconia (YSZ), and a monolithic ceramic, silicon nitride (Si 3 N 4 ). To make the tests more representative of actual hardware, the surface of the CMC was kept in the as-received state (not machined) with the full surface features/roughness present. Test results include: scanning electron microscope characterization of the surfaces, micro-structural characterization, and microprobe analysis.
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