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  • Other Sources  (3)
  • 1990-1994  (3)
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  • 1
    Publication Date: 2019-06-28
    Description: A pressure box test fixture was designed and fabricated to evaluate the effects of internal pressure, biaxial tension loads, curvature, and damage on the fracture response of composite fuselage structure. Previous work in composite fuselage tension damage tolerance, performed during NASA contract NAS1-17740, evaluated the above effects on unstiffened panels only. This work extends the tension damage tolerance testing to curved stiffened fuselage crown structure that contains longitudinal stringers and circumferential frame elements. The pressure box fixture was designed to apply internal pressure up to 20 psi, and axial tension loads up to 5000 lb/in, either separately or simultaneously. A NASTRAN finite element model of the pressure box fixture and composite stiffened panel was used to help design the test fixture, and was compared to a finite element model of a full composite stiffened fuselage shell. This was done to ensure that the test panel was loaded in a similar way to a panel in the full fuselage shell, and that the fixture and its attachment plates did not adversely affect the panel.
    Keywords: COMPOSITE MATERIALS
    Type: NASA. Langley Research Center, Third NASA Advanced Composites Technology Conference, Volume 1, Part 2; p 789-805
    Format: application/pdf
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  • 2
    Publication Date: 2019-07-13
    Description: No abstract available
    Keywords: Exobiology
    Type: Angewandte Chemie (International ed. in English) (ISSN 0570-0833); 29; 2; 183-5
    Format: text
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  • 3
    Publication Date: 2019-07-12
    Description: The rate coefficient for the ion-molecule reaction NH3(+) + H2 yields NH4(+) + H has been calculated as a function of temperature with the use of the statistical phase space approach. The potential surface and reaction complex and transition state parameters used in the calculation have been taken from ab initio quantum chemical calculations. The calculated rate coefficient has been found to mimic the unusual temperature dependence measured in the laboratory, in which the rate coefficient decreases with decreasing temperature until 50-100 K and then increases at still lower temperatures. Quantitative agreement between experimental and theoretical rate coefficients is satisfactory given the uncertainties in the ab initio results and in the dynamics calculations. The rate coefficient for the unusual three-body process NH3(+) + H2 + He yields NH4(+) + H + He has also been calculated as a function of temperature and the result found to agree well with a previous laboratory determination.
    Keywords: ATOMIC AND MOLECULAR PHYSICS
    Type: Journal of Chemical Physics (ISSN 0021-9606); 94; 12:00 PM
    Format: text
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