NASA Scientific and Technical Aerospace Reports

or M60J graphite fibers and PMR-II-50 polyimide resin matrix. The composites were tested as supplied and after
thermo-cycling, with the thermo-cycled composites being tested under dry and wet conditions. Acoustic emission (AE) was
monitored during the room and high temperature Iosipescu experiments. The shear stresses at the maximum loads and the
shear stresses at the significant onset of AE were determined for the composites as function of temperature and conditioning.
The combined effects of thermo-cycling and moisture on the strength and stiffness properties of the composites were
evaluated. It was determined that the room and high temperature shear stresses at the maximum loads were unaffected by
conditioning. However, at room temperature the significant onset of AE was affected by conditioning; the thermal conditioned
wet specimens showed the highest shear stress at the onset of AE followed by thermal-conditioned and then as received
specimens. Also, at igh temperature the significant onset of AE occurred in some specimens after the maximum load due to
the viscoelastoplastic nature of the matrix material.
Author
Fiber Composites; Graphite; Polyimide Resins; Shear Stress; Woven Composites; Modulus of Elasticity; Reinforcing
Materials
20040111286 NASA Glenn Research Center, Cleveland, OH, USA
Advanced Materials and Coatings for Aerospace Applications
Miyoshi, Kazuhisa; [2004]; 2 pp.; In English
Contract(s)/Grant(s): 708-04-04; No Copyright; Avail: CASI; A01, Hardcopy
In the application area of aerospace tribology, researchers and developers must guarantee the highest degree of reliability
for materials, components, and systems. Even a small tribological failure can lead to catastrophic results. The absence of the
required knowledge of tribology, as Professor H.P. Jost has said, can act as a severe brake in aerospace vehicle systems-and
indeed has already done so. Materials and coatings must be able to withstand the aerospace environments that they encounter,
such as vacuum terrestrial, ascent, and descent environments; be resistant to the degrading effects of air, water vapor, sand,
foreign substances, and radiation during a lengthy service; be able to withstand the loads, stresses, and temperatures
encountered form acceleration and vibration during operation; and be able to support reliable tribological operations in harsh
environments throughout the mission of the vehicle. This presentation id divided into two sections: surface properties and
technology practice related to aerospace tribology. The first section is concerned with the fundamental properties of the
surfaces of solid-film lubricants and related materials and coatings, including carbon nanotubes. The second is devoted to
applications. Case studies are used to review some aspects of real problems related to aerospace systems to help engineers and
scientists to understand the tribological issues and failures. The nature of each problem is analyzed, and the tribological
properties are examined. All the fundamental studies and case studies were conducted at the NASA Glenn Research Center.
Author
Aerospace Engineering; Tribology; Coatings; Composite Materials
20040111294 NASA Langley Research Center, Hampton, VA, USA
A Spectral Analysis Approach for Acoustic Radiation from Composite Panels
Turner, Travis L.; Singh, Mahendra P.; Mei, Chuh; [2004]; 10 pp.; In English
Report No.(s): AIAA-95-1303; Copyright; Avail: CASI; A02, Hardcopy
A method is developed to predict the vibration response of a composite panel and the resulting far-field acoustic radiation
due to acoustic excitation. The acoustic excitation is assumed to consist of obliquely incident plane waves. The panel is
modeled by a finite element analysis and the radiated field is predicted using Rayleigh’s integral. The approach can easily
include other effects such as shape memory alloy (SMA) ber reinforcement, large detection thermal postbuckling, and
non-symmetric SMA distribution or lamination. Transmission loss predictions for the case of an aluminum panel excited by
a harmonic acoustic pressure are shown to compare very well with a classical analysis. Results for a composite panel with and
without shape memory alloy reinforcement are also presented. The preliminary results demonstrate that the transmission loss
can be significantly increased with shape memory alloy reinforcement. The mechanisms for further transmission loss
improvement are identified and discussed.
Author
Composite Structures; Far Fields; Panels; Sound Waves; Spectrum Analysis
20040111312 NASA Langley Research Center, Hampton, VA, USA
Augmented Shock Wave Severance of Materials
Bement, Laurence J.; Schimmel, Morry L.; [1995]; 12 pp.; In English; 31st AIAA/ASME/SAE/ASEE Joint Propulsion
Conference and Exhibit, 10-12 Jul. 1995, San Diego, CA, USA
Report No.(s): AIAA Paper 95-2407; Copyright; Avail: CASI; A03, Hardcopy
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