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  • 1
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    Effects of changes in composite lamina properties on laminate coefficient of thermal expansion (1992)
    In:  Other Sources
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    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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  • 2
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    Composite materials for precision space reflector panels (1992)
    In:  Other Sources
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    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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  • 3
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    Residual thermal stresses in composites for dimensionally stable spacecraft applications (1992)
    In:  Other Sources
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    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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  • 4
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    Electron radiation effects on the thermal expansion of graphite resin composites (1986)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Keywords: COMPOSITE MATERIALS
    Type: Journal of Spacecraft and Rockets (ISSN 0022-4650); 23; 625-629
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  • 5
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    Thermal expansion behavior of graphite/glass and graphite/magnesium (1986)
    In:  Other Sources
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    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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  • 6
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    Prediction of coefficients of thermal expansion for unidirectional composites (1989)
    In:  Other Sources
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    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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  • 7
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    Thermal expansion measurements of metal matrix composites (1988)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The laser-interferometric-dilatometer system currently operational at NASA-Langley is described. The system, designed to characterize metal matrix composites, features high precision, automated data acquisition, and the ability to test a wide variety of specimen geometries over temperature ranges within 80-422 K. The paper presents typical thermal-expansion measurement data for a Gr/Al rod; Gr/Al and Gr/Mg unidirectional laminates; and a Gr/Mg (+ or -8)s laminate.
    Keywords: COMPOSITE MATERIALS
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  • 8
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    Stresses and deformations in angle-ply composite tubes (1987)
    In:  CASI
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    Publication Date: 2019-06-28
    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: NASA-TM-89365 , NAS 1.15:89365 , CCMS-87-04 , VPI-E-87-3
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  • 9
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    The development of composite materials for spacecraft precision reflector panels (1990)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: One of the critical technology needs for large precision reflectors required for future astrophysics and optical communications is in the area of structural materials. Therefore, a major area of the Precision Segmented Reflector Program at NASA is to develop lightweight composite reflector panels with durable, space environmentally stable materials which maintain both surface figure and required surface accuracy necessary for space telescope applications. Results from the materials research and development program at NASA Langley Research Center are discussed. Advanced materials that meet the reflector panel requirements are identified. Thermal, mechanical and durability properties of candidate materials after exposure to simulated space environments are compared to the baseline material.
    Keywords: COMPOSITE MATERIALS
    Type: Advances in Optical Structure Systems; Apr 16, 1990 - Apr 19, 1990; Orlando, FL; United States
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  • 10
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    Techniques for measurement of the thermal expansion of advanced composite materials (1989)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: Techniques available to measure small thermal displacements in flat laminates and structural tubular elements of advanced composite materials are described. Emphasis is placed on laser interferometry and the laser interferometric dilatometer system used at the National Aeronautics and Space Administration (NASA) Langley Research Center. Thermal expansion data are presented for graphite-fiber reinforced 6061 and 2024 aluminum laminates and for graphite fiber reinforced AZ91 C and QH21 A magnesium laminates before and after processing to minimize or eliminate thermal strain hysteresis. Data are also presented on the effects of reinforcement volume content on thermal expansion of silicon-carbide whisker and particulate reinforced aluminum.
    Keywords: COMPOSITE MATERIALS
    Type: Symposium on Metal Matrix Composites: Testing, Analysis, and Failure Modes; Apr 25, 1988 - Apr 26, 1988; Sparks, NV; United States
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