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  • Other Sources  (8)
  • COMPOSITE MATERIALS  (4)
  • STRUCTURAL MECHANICS  (4)
  • 1980-1984  (8)
  • 1983  (6)
  • 1982  (2)
  • 1
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    Rubber-toughened polyfunctional epoxies - Brominated vs nonbrominated formulated for graphite composites (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: A new, commercially available, trifunctional epoxy resin (tris-(hydroxyphenyl)-methane triglycidyl ether) was modified with synthetic rubber to increase the impact resistance of epoxy/graphite composites. These composites were reinforced with commercially available satin-weave carbon cloth using two formulations of epoxies (brominated and nonbrominated) containing various amounts of carboxy-terminated butadience acrylonitrile (CTBN) rubber that had been prereacted with epoxy resin. The impact resistance was determined by measuring the interlaminar shear strength of the composites after impact. The mechanical properties, such as flexural strength and modulus at room temperature and at 93 C, were also determined. Measurements were taken of the flammability and glass transition temperature (Tg); and a thermal-gravimetric analysis was made.
    Keywords: COMPOSITE MATERIALS
    Type: SAMPE Quarterly (ISSN 0036-0821); 14; 34-38
    Format: text
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    NASA TECHNICAL REPORTS
  • 2
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    Polyfunctional epoxies - Different molecular weights of brominated polymeric additives as flame retardants in graphite composites (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: The imparting of flame retardancy to graphite-reinforced composites without incurring mechanical property deterioration is investigated for the case of an experimental, trifunctional epoxy resin incorporating brominated polymeric additives (BPAs) of the diglycidyl type. Such mechanical properties as flexural strength and modulus, and short beam shear strength, were measured in dry and in hot/wet conditions, and the glass transition temperature, flammability, and water absorption were measured and compared with nonbromilated systems. Another comparison was made with a tetrafunctional epoxy system. The results obtained are explained in terms of differences in the polymeric backbone length of the bromine carrier polymer. BPAs are found to be a reliable bromine source for fire inhibition in carbon-reinforced composites without compromise of mechanical properties.
    Keywords: COMPOSITE MATERIALS
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    NASA TECHNICAL REPORTS
  • 3
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    Mechanics of composite materials: Recent advances; Proceedings of the Symposium, Virginia Polytechnic Institute and State University, Blacksburg, VA, August 16-19, 1982 (1983)
    In:  Other Sources
    Details
    Publication Date: 2016-03-09
    Description: The present conference on the mechanics of composites discusses microstructure's influence on particulate and short fiber composites' thermoelastic and transport properties, the elastoplastic deformation of composites, constitutive equations for viscoplastic composites, the plasticity and fatigue of metal matrix composites, laminate damping mechanisms, the micromechanical modeling of Kevlar/epoxy composites' time-dependent failure, the variational characterization of waves in composites, and computational methods for eigenvalue problems in composite design. Also discussed are the elastic response of laminates, elastic coupling nonlinear effects in unsymmetrical laminates, elasticity solutions for laminate problems having stress singularities, the mechanics of bimodular composite structures, the optimization of laminated plates and shells, NDE for laminates, the role of matrix cracking in the continuum constitutive behavior of a damaged composite ply, and the energy release rates of various microcracks in short fiber composites.
    Keywords: COMPOSITE MATERIALS
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    NASA TECHNICAL REPORTS
  • 4
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    Propagation of crazing in viscoelastic media (1983)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: In response to a tensile stress glassy polymers exhibit crazing (surface cracks) which is a phenomenon of considerable practical and theoretical importance in the use of many plastics. An attempt is made to demonstrate how craze growth behavior is affected by the craze density (which is defined as the total number of crazes per unit surface area) surrounding the craze.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-CR-173244 , NAS 1.26:173244
    Format: application/pdf
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  • 5
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    Stability, vibration and passive damping of partially restrained imperfect columns (1983)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A theoretical and experimental study of slender tubular columns for possible use in space structures is conducted in the presence of partial rotational end restraints. Explicit formulas are derived for computing the buckling load and the lowest natural frequency of perfectly straight uniform elastic members with rotational end restraints possessing linear moment-rotation characteristics. An exact solution in the form of a transcendental equation, and a numerical solution using second-order finite-differences are also presented. The presence of an initial imperfection is also incorporated into the numerical procedure. Vibration tests are conducted on an imperfect tubular steel member in the absence of an axial load. A damping concept consisting of a string-mass assembly is explored. Three passive damping configurations involving combinations of three lead shots were investigated. The three lead shot configurations provided considerably greater damping than the single lead shot.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-TM-85697 , NAS 1.15:85697
    Format: application/pdf
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  • 6
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    On the three-dimensional vibrations of the cantilevered rectangular parallelepiped (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: A solution is presented for the three-dimensional problem of determining the free vibration frequencies and mode shapes for a rectangular parallelepiped which is completely fixed on one face and free on the other five faces. This problem apparently is previously unsolved in the published literature. The Ritz method is used, with displacements assumed in the form of algebraic polynomials. Convergence is studied. Numerical results are given for the first five frequencies of each of the four symmetry classes of vibration, for five thick parallelepiped configurations, including the cube. Contour plots are exhibited for the modal displacements of the cube. The effects of varying Poisson's ratio are also observed.
    Keywords: STRUCTURAL MECHANICS
    Type: Acoustical Society of America, Journal (ISSN 0001-4966); 73; June 198
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    NASA TECHNICAL REPORTS
  • 7
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    Evaluation of SRB phenolic TPS material made by an alternate vendor (1982)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Tests conducted to evaluate the adequacy of solid rocket booster (SRB) phenolic thermal protection system (TPS) material supplied by an alternate vendor chosen by United Space Boosters, Inc. (USBI), to replace the current phenolic TPS sections used thus far on the first four Shuttle flights. The phenolic TPS is applied mainly to the attach and kick rings of the solid rocket booster (SRB). Full-scale sectional models of both the attach and kick ring structure were made up with 0.0265 in. thick stainless steel thin skin covers with thermocouples on them to determine the heating rates. Such models were made up for both the forward and rear faces of the kick ring which has a different configuration on each side. The thin skins were replaced with the alternate phenolic TPS sections cut from flight hardware configuration phenolic parts as supplied by the new vendor. Two tests were performed for each configuration of the attach and kick rings and the samples were exposed to the flow for a duration that gave a heat load equivalent to that obtained in the series of runs made for the current line of phenolic TPS. The samples performed very well with no loss of any phenolic layers. The post-test samples looked better than those used to verify the current phenolic TPS.
    Keywords: COMPOSITE MATERIALS
    Type: NASA-CR-170894 , NAS 1.26:170894 , LMSC-HREC-TN-D867581
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    NASA TECHNICAL REPORTS
  • 8
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    Study of NSI and related cable performance during tests performed in the NASA Hot Gas Facility (1982)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Some seven different configurations of the NSI and other cables were tested in the NASA-MSFC Hot Gas Facility (HGF). The tests were conducted to study what happens to the cables when they are exposed to hot flow as was the case in the first two Shuttle flights, the STS-1 and STS-2. Protection of these components is vital for various functions especially to attain proper nozzle separation. The tests in the HGF demonstrated the severity of the aerodynamic forces combined with aero heating environment on the test cables and helped, in general, to evaluate the cable wrap materials and cable mounting hardware and technique. Blastape 2 cable wrap which is adequate for thermal protection of the cables must be properly clamped at its ends. The nylon clamps (or ties) used to secure cables to metal components inside the skirt could not withstand the heating. K5NA closeout material used on the outboard surface of the aft skirt when troweled over the cables performed excellently in protecting the cables and mounting hardware.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-CR-170886 , NAS 1.26:170886 , LMSC-HREC-TM-D784644
    Format: application/pdf
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