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Full-Text Articles in Engineering
Static Fatigue Of Hi-Nicalon™ S Ceramic Fiber Tows At 600°C In Air And Silicic Acid-Saturated Steam, Caleigh M. Nelson
Static Fatigue Of Hi-Nicalon™ S Ceramic Fiber Tows At 600°C In Air And Silicic Acid-Saturated Steam, Caleigh M. Nelson
Theses and Dissertations
Ceramic matrix composites (CMCs) have the potential to be utilized in applications such as hypersonic vehicles, aircraft leading edges, hot sections of engines, and rocket nozzles. Of particular interest are advanced SiC/SiC composites that can withstand the elevated temperatures and harsh oxidizing environments while maintaining their properties and structural integrity under an applied load. Steam, a major component of combustion environment, is one such aggressive oxidizing environment. As steam passes through the SiC/SiC composite, entering the composite interior through the cracks in the SiC matrix, it becomes saturated with silicic acid, Si(OH)4. Before incorporating SiC/SiC composites in the …
Creep Of Hi-Nicalon™ S Ceramic Fiber Tows At 800°C In Air And In Silicic Acid-Saturated Steam, Scott J. Robertson
Creep Of Hi-Nicalon™ S Ceramic Fiber Tows At 800°C In Air And In Silicic Acid-Saturated Steam, Scott J. Robertson
Theses and Dissertations
A facility was demonstrated that successfully resolved problems highlighted by previous attempts to study SiC fibers in steam. Monotonic tension and creep tests were conducted to characterize the fibers. The tensile strength of the fibers showed little dependence on applied stress rate, indicating a resistance to environmentally assisted crack growth. Climb-controlled diffusion in air and grain boundary sliding in silicic acid-saturated steam were the dominant damage mechanisms. Silicic acid-saturated steam had a degrading effect on the mechanical performance of the fibers, but much less than unsaturated steam environments. The Monkman-Grant relationship was demonstrated for Hi-NicalonTM S fibers and may be …
Tension-Compression Fatigue Of An Oxide/Oxide Ceramic Matrix Composite At Elevated Temperature In Air And Steam Environments, Richard L. Lanser
Tension-Compression Fatigue Of An Oxide/Oxide Ceramic Matrix Composite At Elevated Temperature In Air And Steam Environments, Richard L. Lanser
Theses and Dissertations
Tension-compression fatigue behavior of an oxide-oxide ceramic matrix composite was investigated at 1200°C in air and steam. The composite is comprised of an alumina matrix reinforced with Nextel 720 fibers woven in an eight harness satin weave. The composite relies on a porous matrix for damage tolerance. Compression and tension tests to failure were conducted to characterize basic mechanical properties. Tension-compression fatigue tests were performed at 1 Hz frequency with a ratio of minimum to maximum stress of -1. Maximum stresses ranged from 60-120 MPa. Fatigue run-out (defined as 105 cycles) was achieved in air at 80 MPa and in …
Effect Of Prior Exposure At Elevated Temperatures On Tensile Properties And Stress-Strain Behavior Of Three Oxide/Oxide Ceramic Matrix Composites, Christopher J. Hull
Effect Of Prior Exposure At Elevated Temperatures On Tensile Properties And Stress-Strain Behavior Of Three Oxide/Oxide Ceramic Matrix Composites, Christopher J. Hull
Theses and Dissertations
Thermal stability of three oxide-oxide ceramic matrix composites was studied. The materials studied were NextelTM610/aluminosilicate (N610/AS), NextelTM720/aluminosilicate (N720/AS), and NextelTM720/Alumina (N720/A), commercially available oxide-oxide ceramic composites (COI Ceramics, San Diego, CA). The N610/AS composite consists of a porous aluminosilicate matrix reinforced with laminated woven alumina N610 fibers. The N720/AS and N720/A composites consist of a porous oxide matrix reinforced with laminated, woven mullite/alumina (NextelTM720) fibers. The matrix materials are aluminosilicate in N720/AS and alumina in N720/A. All three composites have no interface between the fibers and matrix, and rely on the porous …
Creep Behavior In Interlaminar Shear Of A Cvi Sic/Sic Composite At Elevated Temperatures In Air And Steam, Matthew T. Pope
Creep Behavior In Interlaminar Shear Of A Cvi Sic/Sic Composite At Elevated Temperatures In Air And Steam, Matthew T. Pope
Theses and Dissertations
This research investigated the interlaminar shear performance of a SiC/SiC ceramic matrix composite. The interlaminar shear performance was observed in compression of double notched specimens (DNS) at 1200°C in both laboratory air and in steam. Compression to failure tests determined the as-processed interlaminar shear strength and interlaminar shear creep tests were conducted with stresses ranging from -22 MPa to -16 MPa. Primary and secondary creep regimes were observed in all creep tests. The specimens tested in creep at -16 MPa in air achieved run-out, defined as 100 hours at creep stress. The residual strength decreased slightly after 100 h of …
Creep Of Hi-Nicalon S Ceramic Fiber Tows At Elevated Temperature In Air And In Steam, Benjamin R. Steffens
Creep Of Hi-Nicalon S Ceramic Fiber Tows At Elevated Temperature In Air And In Steam, Benjamin R. Steffens
Theses and Dissertations
Structural aerospace components require materials to have superior long-term mechanical properties that can withstand severe environmental conditions, such as high temperatures, high pressures and moisture, whilst enduring the loads they are designed for. Ceramic-matrix composites (CMCs) are capable of maintaining excellent strength and creep resistance at high temperatures, which make them attractive candidate materials for aerospace applications, particularly in propulsion. Silicon Carbide (SiC) ceramic fibers have been used as constituent materials in CMCs, although oxidation of the SiC to SiO2 has been a known degredation mechanism. Recently developed near stoichiometric SiC fibers have shown significant improvements in thermochemical stability; …