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  • 1
    Publication Date: 2011-08-24
    Description: An overview of NASA LaRC's research on thermal residual stresses and their effect on the dimensional stability of carbon fiber reinforced polymer-matrix composites is presented. The data show that thermal residual stresses can induce damage in polymer matrix composites and significantly affect the dimensional stability of these composites by causing permanent residual strains and changes in CTE. The magnitude of these stresses is primarily controlled by the laminate configuration and the applied temperature change. The damage caused by thermal residual stresses initiates at the fiber/matrix interface and micromechanics level analyses are needed to accurately predict it. An increased understanding of fiber/matrix interface interactions appears to be the best approach for improving a composite's resistance to thermally induced damage.
    Keywords: COMPOSITE MATERIALS
    Type: In: International Congress on Experimental Mechanics, 7th, Las Vegas, NV, June 8-11, 1992, Proceedings. Vol. 2 (A94-12901 02-39); p. 1211-1219.
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  • 2
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    In:  CASI
    Publication Date: 2013-08-31
    Description: In summary, advantages of the ablative thermal protection system (TPS) for aerobrakes are: (1) proven reliable TPS systems; (2) well characterized (thermally) with good, existing thermal analysis capability; (3) good candidate materials are available; (4) not sensitive to defects and more difficult to damage then RSI or C-C; (5) design program which demonstrated simple (direct bond) application of large panels; (6) thermal excursions not catastrophic; and (7) no SIP required.
    Keywords: SPACE TRANSPORTATION
    Type: Space Transportation Materials and Structures Technology Workshop. Volume 2: Proceedings; p 369-373
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  • 3
    Publication Date: 2013-08-31
    Description: The results of the Trapped Radiation Effects Panel for the Space Environmental Effects on Materials Workshop are presented. The needs of the space community for new data regarding effects of the space environment on materials, including electronics are listed. A series of questions asked of each of the panels at the workshop are addressed. Areas of research which should be pursued to satisfy the requirements for better knowledge of the environment and better understanding of the effects of the energetic charged particle environment on new materials and advanced electronics technology are suggested.
    Keywords: CHEMISTRY AND MATERIALS (GENERAL)
    Type: NASA(SDIO Space Environmental Effects on Materials Workshop, Part 2; p 597-605
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  • 4
    Publication Date: 2013-08-31
    Description: The stress and deformations in angle-ply composite tubes subjected to axisymmetric thermal loading were investigated both experimentally and analytically. For the theoretical portion a generalized plane strain elasticity analysis was developed. The analysis included mechanical and thermal loading, and temperature-dependent material properties. The elasticity analysis was also used to study the effect of including a thin metallic coating on a graphite-epoxy tube. The stresses in the coatings were found to be quite high, exceeding the yield stress of aluminum. An important finding in the analytical studies was the fact that even tubes with a balanced-symmetric lamination sequence exhibit shear deformation, or twist. For the experimental portion an apparatus was developed to measure torsional and axial response in the temperature range of 140 to 360 K. Eighteen specimens were tested, combining three material systems, eight lamination sequences, and three off-axis ply orientation angles. For the twist response, agreement between analysis and experiment was found to be good. The axial response of the tubes tested was found to be greater than predicted by a factor of three. As a result, it is recommended that the thermally induced axial deformations be investigated, both experimentally and analytically.
    Keywords: COMPOSITE MATERIALS
    Type: VPI-E-87-3 , NASA-TM-89365 , CCMS-87-04 , NAS 1.15:89365
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  • 5
    Publication Date: 2013-08-31
    Description: The effects of thermal cycling on the thermal and mechanical properties of composite materials that are candidates for space structures are briefly described. The results from a thermal analysis of the orbiting Space Station Freedom is used to define a typical thermal environment and the parameters that cause changes in the thermal history. The interactions of this environment with composite materials are shown and described. The effects of this interaction on the integrity as well as the properties of GR/thermoset, Gr/thermoplastic, Gr/metal and Gr/glass composite materials are discussed. Emphasis is placed on the effects of the interaction that are critical to precision spacecraft. Finally, ground test methodology are briefly discussed.
    Keywords: SPACECRAFT DESIGN, TESTING AND PERFORMANCE
    Type: NASA(SDIO Space Environmental Effects on Materials Workshop, Part 2; p 447-470
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  • 6
    Publication Date: 2011-08-24
    Description: One of the critical technology needs of large precision reflectors for future astrophysical and optical communications satellites lies in the area of structural materials. Results from a materials research and development program at NASA Langley Research Center to provide materials for these reflector applications are discussed. Advanced materials that meet the reflector panel requirements are identified, and thermal, mechanical and durability properties of candidate materials after exposure to simulated space environments are compared. A parabolic, graphite-phenolic honeycomb composite panel having a surface accuracy of 70.8 microinches rms and an areal weight of 1.17 lbm/sq ft was fabricated with T50/ERL1962 facesheets, a PAEI thermoplastic surface film, and Al and SiO(x) coatings.
    Keywords: COMPOSITE MATERIALS
    Type: In: Design of optical instruments; Proceedings of the Meeting, Orlando, FL, Apr. 22-24, 1992 (A93-29781 11-74); p. 250-261.
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  • 7
    Publication Date: 2011-08-19
    Description: Several analyses for predicting the longitudinal, alpha(1), and transverse, alpha(2), coefficients of thermal expansion of unidirectional composites were compared with each other, and with experimental data on different graphite fiber reinforced resin, metal, and ceramic matrix composites. Analytical and numerical analyses that accurately accounted for Poisson restraining effects in the transverse direction were in consistently better agreement with experimental data for alpha(2), than the less rigorous analyses. All of the analyses predicted similar values of alpha(1), and were in good agreement with the experimental data. A sensitivity analysis was conducted to determine the relative influence of constituent properties on the predicted values of alpha(1), and alpha(2). As would be expected, the prediction of alpha(1) was most sensitive to longitudinal fiber properties and the prediction of alpha(2) was most sensitive to matrix properties.
    Keywords: COMPOSITE MATERIALS
    Type: Journal of Composite Materials (ISSN 0021-9983); 23; 370-388
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  • 8
    Publication Date: 2011-08-19
    Description: The thermal expansion behavior of n (+/- 8)s graphite fiber reinforced magnesium laminate and four graphite reinforced glass-matrix laminates (a unidirectional laminate, a quasi-isotropic laminate, a symmetric low angle-ply laminate, and a random chopped-fiber mat laminate) was determined, and was found, in all cases, to not be significantly affected by thermal cycling. Specimens were cycled up to 100 times between -200 F and 100 F, and the thermal expansion coefficients determined for each material as a function of temperature were found to be low. Some dimensional changes as a function of thermal cycling, and some thermal-strain hysteresis, were observed.
    Keywords: COMPOSITE MATERIALS
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  • 9
    Publication Date: 2011-08-19
    Keywords: COMPOSITE MATERIALS
    Type: Journal of Spacecraft and Rockets (ISSN 0022-4650); 23; 625-629
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  • 10
    Publication Date: 2011-08-24
    Description: An analytical study of the effects of changes in composite lamina properties on the laminate coefficient of thermal expansion, CTE, has been made. Low modulus graphite/epoxy (T300/934) and high modulus graphite/epoxy (P75/934, P100/934, P120/934), graphite/aluminum (P100/Al), and graphite/glass (HMS/Gl) composite materials were considered in quasi-isotropic and near-zero CTE laminate configurations. The effects of changes in lamina properties on the laminate CTE strongly depend upon the type of composite material as well as the laminate configuration. A 10 percent change in the lamina transverse CTE resulted in changes as large as 0.22 ppm/C in the laminate CTE of a quasi-isotropic Gr/934 laminates. No significant differences were observed in the sensitivities of the laminate CTEs of the P100/934 and P120/934 composite materials due to identical changes in lamina properties. Large changes in laminate CTE can also result from measured temperature and radiation effects on lamina properties.
    Keywords: COMPOSITE MATERIALS
    Type: In: International SAMPE Technical Conference, 24th and International SAMPE Metals and Metals Processing Conference, 3rd, Toronto, Canada, Oct. 20-22, 1992, Proceedings. Vol. 24 (A93-53376 23-23); p. T867-T878.
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