NASA Scientific and Technical Aerospace Reports

20040111387 Army Research Lab., Cleveland, OH, USA
Oxidation Kinetics and Strength Degradation of Carbon Fibers in a Cracked Ceramic Matrix Composite
Halbig, Michael C.; [2003]; 42 pp.; In English; 28th International Cocoa Beach Conference and Exposition on Advanced
Ceramics and Composites, 25-30 Jan. 2003, Cocoa Beach, Fl, USA
Contract(s)/Grant(s): 708-73-10; No Copyright; Avail: CASI; A03, Hardcopy
Experimental results and oxidation modeling will be presented to discuss carbon fiber susceptibility to oxidation, the
oxidation kinetics regimes and composite strength degradation and failure due to oxidation. Thermogravimetric Analysis
(TGA) was used to study the oxidation rates of carbon fiber and of a pyro-carbon interphase. The analysis was used to
separately obtain activation energies for the carbon constituents within a C/SiC composite. TGA was also conducted on C/SiC
composite material to study carbon oxidation and crack closure as a function of temperature. In order to more closely match
applications conditions C/SiC tensile coupons were also tested under stressed oxidation conditions. The stressed oxidation
tests show that C/SiC is much more susceptible to oxidation when the material is under an applied load where the cracks are
open and allow for oxygen ingress. The results help correlate carbon oxidation with composite strength reduction and failure.
Derived from text
Ceramic Matrix Composites; Cracks; Oxidation; Reaction Kinetics; Matrix Materials; Silicon Carbides
20040111388 NASA Glenn Research Center, Cleveland, OH, USA
An Assessment of Variability in the Average Tensile Properties of a Melt-Infiltrated SiC/SiC Composite
Kalluri, Sreeramesh; Brewer, David N.; Calomino, Anthony M.; [2004]; 8 pp.; In English; 28th International Cocoa Beach
Conference and Exposition on Advance Ceramics and Composites, 25-30 Jan. 2004, Cocoa Beach, FL, USA
Contract(s)/Grant(s): NCC3-1041; No Copyright; Avail: CASI; A02, Hardcopy
Woven SiC/SiC Ceramic Matrix Composites (CMCs), manufactured by the slurry-cast, melt-infiltration process are under
consideration as combustor liner materials in aircraft gas turbine engines. Tensile properties (elastic modulus, proportional
limit strength, in-plane tensile strength and strain to failure) of the CMC, manufactured during two separate time periods (9/99
and 1/01) were determined at 816 and 1024 C by conducting tensile tests on specimens machined from the CMC plates. A
total of 24 tensile tests were conducted for each temperature and CMC variant combination. In this study average tensile
properties of the two cMC variants were statistically compared to evaluate significant differences, if any, within the CMC’s
properties.
Derived from text
Ceramic Matrix Composites; Modulus of Elasticity; Tensile Properties; Tensile Tests; Silicon Carbides
20040111389 NASA Glenn Research Center, Cleveland, OH, USA
Foreign Object Damage Behavior of a SiC/SiC Composite at Ambient and Elevated Temperatures
Bhatt, Ramakrishna T.; Pereira, J. Michael; Gyekenyesi, John P.; Choi, Sung R.; [2004]; 8 pp.; In English; ASME Turbo Expo
2004: Power for Land, Sea, and Air, 14-17 Jun. 2004, Vienna,, Austria
Contract(s)/Grant(s): 714-30-19
Report No.(s): GT2004-53910; No Copyright; Avail: CASI; A02, Hardcopy
Foreign object damage (FOD) behavior of a gas-turbine grade SiC/SiC ceramic matrix composite (CMC) was determined
at 25 and 1316 C, employing impact velocities from 115 to 440 meters per second by 1.59-mm diameter stell-ball projectiles.
Two different types of specimen support were used at each temperature: fully supported and partially supported. For a given
temperature, the degree of post-impact strength degradation increased with increasing impact velocity, and was greater in a
partially supported configuration than in a fully supported one. The elevated-temperature FOD resistance of the composite,
particularly under partially supported loading at higher impact velocities greater than or equal to 350 meters per second, was
significantly less than the ambient-temperature counterpart, attributed to a weakening effect of the composite. For fully
supported loading, frontal contact stress played a major role in generating composite damage; whereas, for partially supported
loading, both frontal contact and backside bending stresses were combined sources of damage generation. The SiC/SiC
composite was able to survive higher energy impacts without complete structural failure but suffered more strength affecting
damage from low energy impacts than AS800 and SN282 silicon nitrides.
Author
Ambient Temperature; Damage; Silicon Carbides; Ceramic Matrix Composites; High Temperature; Mechanical Properties;
Foreign Bodies
56