NASA Scientific and Technical Aerospace Reports

is still important, the industry’s future prime contractors will be lead systems integrators who are able to deal with increasingly
complex platforms and systems-of-systems. One weakness of the vision creating some uncertainty in the industry has been
airlift requirements for this transformed force, which still exceed projected capabilities and warrant clarification by the
Department of Defense. For the foreseeable future, the U.S. LCS Industry will be critical to meeting U.S. national security
needs, necessitating continued close government stewardship. Dilemmas faced by such stewardship include deciding on the
degree of foreign participation allowed by U.S. LCS firms and weighing LCS firms implementation of lean manufacturing
techniques, necessary for their economic viability, against the nation s need for surge production in the event of emergencies.
Although the LCS Industry faces challenges in coming years, its opportunities for growth appear to remain significant.
DTIC
Combat; Warfare
20040111961 Ohio Aerospace Inst., Cleveland, OH, USA
Melt-Infiltrated SiC Composites for Gas Turbine Engine Applications
Morscher, Gregory N.; Pujar, Vijay V.; [2004]; 7 pp.; In English; ASME Turbo Expo Land, Sea and Air 2004, 14-17 Jun.
2004, Vienna, Austria
Contract(s)/Grant(s): NCC3-763; 714-04-10
Report No.(s): GT2004-53196; Copyright; Avail: CASI; A02, Hardcopy
SiC-SiC ceramic matrix composites (CMCs) manufactured by the slurry -cast melt-infiltration (MI) process are leading
candidates for many hot-section turbine engine components. A collaborative program between Goodrich Corporation and
NASA-Glenn Research Center is aimed at determining and optimizing woven SiC/SiC CMC performance and reliability. A
variety of composites with different fiber types, interphases and matrix compositions have been fabricated and evaluated.
Particular focus of this program is on the development of interphase systems that will result in improved intermediate
temperature stressed-oxidation properties of this composite system. The effect of the different composite variations on
composite properties is discussed and, where appropriate, comparisons made to properties that have been generated under
NASA’s Ultra Efficient Engine Technology (UEET) Program.
Author
Ceramic Matrix Composites; Silicon Carbides; Fibers; Temperature; Oxidation; Gas Turbine Engines
20040111966 NASA Langley Research Center, Hampton, VA, USA
Stress Dependence of Ultrasonic Velocity in Unidirectional Graphite/Epoxy Composites for Longitudinal Waves
Propagating Along the Direction of Stress
Prosser, William H.; Revire of Progress in Quantitative Nondestructive Evaluation; [1990]; Volume 9, pp. 1701-1707; In
English; Original contains black and white illustrations; No Copyright; Avail: CASI; A02, Hardcopy
The first measurements of the stress induced velocity changes for propagation directions along the direction of applied
stress in gr/ep composites have been presented. For propagation and stress direction perpendicular to the fiber direction, the
data demonstrated a linear relation between normalized velocity shift and stress. After corrections for the delay line were
made, the slope or SAC was determined and compared favorably with the expected value calculated from the previously
determined nonlinear coefficients of this material. The ratio of the SAC to the elastic compliance for this direction of loading
was evaluated and found to have a value similar to numerous other materials which have very different linear elastic properties.
Measurements with stress and propagation along the fibers yielded unusual behavior. The curves were very nonlinear and even
shifted direction at higher loads. The large scatter in the data due to bond variations made separation of material effects from
bond induced artifacts impossible. Thus the SAC, R, and the remaining two unknown TOEC’s could not be determined for
this direction of propagation. These measurements further expand the basis of determining nonlinear elastic properties of
composite materials. These properties may be useful in developing much needed NDE techniques to determine such important
parameters as residual stress after cure and residual strength after impact damage. Additional study is needed to measure the
nonlinear behavior in other composite materials including angle ply laminates. Also, other techniques to measure elastic
nonlinearity such as harmonic generation should be applied to composites to improve the understanding of these properties
and their importance.
Derived from text
Graphite-Epoxy Composites; Longitudinal Waves; Stress Measurement; Ultrasonics
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