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  • 1
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    An instrumented fastener for shear force measurements in joints (1994)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: A preliminary investigation has been conducted on instrumented fasteners for use as sensors to measure the shear loads transmitted by individual fasteners installed in double-splice joints. Calibration and load verification tests were conducted for instrumented fasteners installed at three fastener torque levels. Results from calibration tests show that the shear strains obtained from the instrumented fasteners vary linearly with the applied load and that the instrumented fasteners can be effectively used to measure shear loads transmitted by individual fasteners installed in double-splice joints. Tests were also conducted with three instumented fasteners installed in a typical double-splice joint. The test results showed that the load distribution between individual fasteners is dependent on the location of the fastener in the joint and the fastener torque level.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Experimental Mechanics (ISSN 0014-4851); 34; 1; p. 16-22
    Format: text
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  • 2
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    An investigation of the Iosipescu and Asymmetrical Four-Point Bend tests for composite materials (1985)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: The results of an extensive analytical and experimental investigation of the Iosipescu and Asymmetrical Four-Point Bend (AFPB) test methods are summarized. Finite element analyses were used to assess the influence of notch parameters and load locations on the stress state in the specimens. The shear moduli and shear strengths were experimentally measured for quasi-isotropic graphite-epoxy laminates using both the Iosipescu and the AFPB test methods with various combinations of notch parameters and load locations. The test results indicate that changes in the notch geometry and load locations aimed at improving the stress distribution in the test section result in unexpected changes in the failure mode.
    Keywords: COMPOSITE MATERIALS
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  • 3
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    Derivation and test of elevated temperature thermal-stress-free fastener concept (1985)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Future aerospace vehicles must withstand high temperatures and be able to function over a wide temperature range. New composite materials are being developed for use in designing high-temperature lightweight structures. Due to the difference between coefficients of thermal expansion for the new composite materials and conventional high-temperature metallic fasteners, innovative joining techniques are needed to produce tight joints at all temperatures without excessive thermal stresses. A thermal-stress-free fastening technique is presented that can be used to provide structurally tight joints at all temperatures even when the fastener and joined materials have different coefficients of thermal expansion. The derivation of thermal-stress-free fasteners and joint shapes is presented for a wide variety of fastener materials and materials being joined together. Approximations to the thermal-stress-free shapes that result in joints with low-thermal-stresses and that simplify the fastener/joint shape are discussed. The low-thermal-stress fastener concept is verified by thermal and shear tests in joints using oxide-dispersion-strengthened alloy fasteners in carbon-carbon material. The test results show no evidence of thermal stress damage for temperatures up to 2000 F and the resulting joints carried shear loads at room temperature typical of those for conventional joints.
    Keywords: MECHANICAL ENGINEERING
    Type: Welding, Bonding and Fastening, 1984; p 105-122
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  • 4
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    Effect of stitching on the strength of bonded composite single lap joints (1985)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Keywords: STRUCTURAL MECHANICS
    Type: AIAA Journal (ISSN 0001-1452); 23; 1744-174
    Format: text
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  • 5
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    Effect of simulated mission loads on orbiter thermal protection system undensified tiles (1984)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Keywords: SPACECRAFT DESIGN, TESTING AND PERFORMANCE
    Type: Journal of Spacecraft and Rockets (ISSN 0022-4650); 21; 441-447
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  • 6
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    Mechanical properties of the Shuttle Orbiter thermal protection system strain isolator pad (1984)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: Previously cited in issue 19, p. 2029, Accession no. A82-30079
    Keywords: SPACECRAFT DESIGN, TESTING AND PERFORMANCE
    Type: Journal of Spacecraft and Rockets (ISSN 0022-4650); 21; 253-260
    Format: text
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  • 7
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    Life considerations of the shuttle orbiter densified-tile thermal protection system (1983)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The Shuttle orbiter themal protection system (TPS) incorporates ceramic reusable surface insulation tiles bonded to the orbiter substructure through a strain isolation pad. Densification of the bonding surface of the tiles increases the static strength of the tiles. The densification proces does not, however, necessarily lead to an equivalent increase in fatigue strength. Investigation of the expected lifetime of densified tile TPS under both sinusoidal loading and random loading simulating flight conditions indicates that the strain isolation pads are the weakest components of the TPS under fatigue loading. The felt pads loosen under repetitive loading and, in highly loaded regions, could possibly cause excessive step heights between tiles causing burning of the protective insulation between tiles. A method of improving the operational lifetime of the TPS by using a strain isolation pad with increased stiffness is presented as is the consequence of the effect of increased stiffness on the tile inplane strains and transverse stresses.
    Keywords: SPACE TRANSPORTATION
    Type: Shuttle Performance: Lessons Learned, Pt. 2; p 1009-1024
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  • 8
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    Aerodynamic characteristics of tension shell shapes at Mach 3.0 (1966)
    In:  CASI
    Details
    Publication Date: 2019-05-30
    Description: Aerodynamic characteristics of tension shell shapes at supersonic speed
    Keywords: AERODYNAMICS
    Type: NASA-TN-D-3633
    Format: application/pdf
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  • 9
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    Pressure and heating-rate distributions on a corrugated surface in a supersonic turbulent boundary layer (1977)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Drag and heating rates on wavy surfaces typical of current corrugated plate designs for thermal protection systems were determined experimentally. Pressure-distribution, heating-rate, and oil-flow tests were conducted in the Langley Unitary Plan wind tunnel at Mach numbers of 2.4 and 4.5 with the corrugated surface exposed to both thick and thin turbulent boundary layers. Tests were conducted with the corrugations at cross-flow angles from 0 deg to 90 deg to the flow. Results show that for cross-flow angles of 30 deg or less, the pressure drag coefficients are less than the local flat-plate skin-friction coefficients and are not significantly affected by Mach number, Reynolds number, or boundary-layer thickness over the ranges investigated. For cross-flow angles greater than 30 deg, the drag coefficients increase significantly with cross-flow angle and moderately with Reynolds number. Increasing the Mach number causes a significant reduction in the pressure drag. The average and peak heating penalties due to the corrugated surface are small for cross-flow angles of 10 deg or less but are significantly higher for the larger cross-flow angles.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-TP-1024 , L-11732 , NAS 1.60:1024
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  • 10
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    Room temperature mechanical properties of shuttle thermal protection system materials (1980)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Tests were conducted at room temperature to determine the mechanical properties and behavior of materials used for the thermal protection system of the space shuttle. The materials investigated include the LI-900 RSI tiles, the RTV-560 adhesive and the .41 cm (.16 thick) strain isolator pad (SIP). Tensile and compression cyclic loading tests were conducted on the SIP material and stress-strain curves obtained for various proof loads and load cyclic conditioning. Ultimate tensile and shear tests were conducted on the RSI, RTV, and SIP materials. The SIP material exhibits highly nonlinear stress-strain behavior, increased tangent modulus and ultimate tensile strength with increased loading rate, and large short time load relaxation and moderate creep behavior. Proof and cyclic load conditioning of the SIP results in permanent deformation of the material, hysteresis effects, and much higher tensile tangent modulus values at large strains.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-TM-81786
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