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  • 1
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    An apparatus for bearing-bypass testing of bolted joints (1990)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: A dual-control test system measuring the strength of graphite/epoxy specimens under tension and compression for a wide range of bearing-bypass load ratios is presented. The bearing-bypass strengths of single-fastener specimens are measured for damage onset and ultimate failure and are plotted against one another. The results indicate that an initiated damage grows to failure in the same mode for most cases. However, if the damage is initiated in the compression-reacted-bearing mode, the specimens fail in the offset-compression mode. It is concluded that this type of transition can occur in multi-fastener joints under compression and complicate the strength predictions.
    Keywords: STRUCTURAL MECHANICS
    Type: Experimental Techniques (ISSN 0732-8818); 14; 54-57
    Format: text
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  • 2
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    Stress analysis method for a clearance-fit bolt under bearing loads (1986)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Keywords: STRUCTURAL MECHANICS
    Type: AIAA Journal (ISSN 0001-1452); 24; 1348-135
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  • 3
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    Failure analysis of a graphite/epoxy laminate subjected to bolt-bearing loads (1986)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Quasi-isotropic graphite-epoxy laminates (T300/5208) were tested under bolt bearing loads to study failure modes, strengths, and failure energy. Specimens had a range of configurations to produce failures by the three nominal failure modes: tension, shearout, and bearing. Radiographs were made after damage onset and after ultimate load to examine the failure modes. Also, the laminate stresses near the bolt hole calculated for each test specimen configuration, and then used with a failure criterion to analyze the test data. Failures involving extensive bearing damage were found to dissipate significantly more energy than tension dominated failures. The specimen configuration influenced the failure modes and therefore also influenced the failure energy. In the width-to-diameter ratio range of 4 to 5, which is typical of structural joints, a transition from the tension mode to the bearing mode was shown to cause a large increase in failure energy. The failure modes associated with ultimate strength were usually different from those associated with the damage onset. Typical damage sequences involved bearing damage onset at the hole boundary followed by tension damage progressing from the hole boundary.
    Keywords: COMPOSITE MATERIALS
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  • 4
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    Energy dissipation associated with crack extension in an elastic-plastic material (1987)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Crack extension in elastic-plastic material involves energy dissipation through the creation of new crack surfaces and additional yielding around the crack front. An analytical procedure, using a two-dimensional elastic-plastic finite element method, was developed to calculate the energy dissipation components during a quasi-static crack extension. The fracture of an isotropic compact specimen was numerically simulated using the critical crack-tip-opening-displacement (CTOD) growth criterion. Two specimen sizes were analyzed for three values of critical CTOD. Results from the analysis showed that the total energy dissipation rate consisted of three components: the crack separation energy rate, the plastic energy dissipation rate, and the residual strain energy rate. All three energy dissipation components and the total energy dissipation rate initially increased with crack extension and finally reached constant values.
    Keywords: STRUCTURAL MECHANICS
    Type: Engineering Fracture Mechanics (ISSN 0013-7944); 28; 3, 19; 319-330
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  • 5
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    A survey of strength analysis methods for laminates with holes (1984)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The methods for predicting the strength of composite laminates with fastener holes are reviewed for the cases of unloaded as well as loaded holes. Three categories of methods are discussed: (1) the hole-boundary stress (HBS) methods which compare the peak stresses and the laminate strength; (2) the linear elastic fracture (LEFM) methods which assume cracks emanating from the hole and predict failure when the stress intensity factor for a crack equals the laminate fracture toughness; and (3) two different two-parameter (TP) methods: the average-stress (ASTP) method, which predicts failure when the average stress over a distance from the hole equals the laminate strength; and the point-stress (PSTP) Whitney-Nuismer (1974) approach, which predicts failure when the stress near the hole equals the material strength. The PSTP is relatively accurate and is by far the most widely used of all the prediction methods. However, for large ranges of variables and cases, the current strength predictions may not always be accurate.
    Keywords: STRUCTURAL MECHANICS
    Type: Aeronautical Society of India, Journal (ISSN 0001-9267); 36; 287-303
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  • 6
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    A study of cyclic plastic stresses at a notch root. (1966)
    In:  Other Sources
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    Publication Date: 2011-08-11
    Description: Cyclic plastic stresses at notch roots in aluminum alloy sheet specimens under constant- amplitude repeated tension and reversed loading
    Keywords: STRUCTURAL MECHANICS
    Type: /SOCIETY FOR EXPERIMENTAL STRESS ANALYSIS
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  • 7
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    An equation for bolt clampup relaxation in transient environments (1982)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: (Previously announced in STAR as N82-25327)
    Keywords: COMPOSITE MATERIALS
    Type: Composites Technology Review; 4; Winter 1
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  • 8
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    Bolt clampup relaxation in a graphite/epoxy laminate (1983)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: A simple bolted joint was analyzed to calculate bolt clampup relaxation for a graphite/epoxy (T300/5208) laminate. A viscoelastic finite element analysis of a double-lap joint with a steel bolt was conducted. Clampup forces were calculated for various steady-state temperature-moisture conditions using a 20-year exposure duration. The finite element analysis predicted that clampup forces relax even for the room-temperature-dry condition. The relaxations were 8, 13, 20, and 30 percent for exposure durations of 1 day, 1 month, 1 year, and 20 years, respectively. As expected, higher temperatures and moisture levels each increased the relaxation rate. The combined viscoelastic effects of steady-state temperature and moisture appeared to be additive. From the finite-element analysis, a simple equation was used to calculate clampup forces for the same temperature-moisture conditions as used in the finite-element analysis. The two sets of calculated results agreed well. Previously announced in STAR as N82-19320
    Keywords: COMPOSITE MATERIALS
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  • 9
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    Strain energy release rate distributions for double cantilever beam specimens (1991)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: A 24-ply composite double cantilever-beam specimen under mode I (opening) loading has been analyzed by a 3D FEM code that calculated along a straight delamination starter for several different specimen materials. An isotropic specimen was found to have a strain-energy release rate distribution which varied along its delamination front due to the boundary-layer effect and another effect associated with the anticlastic curvature of the bent specimen arms. A 0-deg graphite-reinforced epoxy specimen had a nearly-uniform strain-energy release rate distribution which dropped only near the edge, due to the boundary-layer effect, and a +/- 45-deg graphite/epoxy specimen exhibited a pronounced strain-energy release rate variation across the specimen width.
    Keywords: STRUCTURAL MECHANICS
    Type: AIAA Journal (ISSN 0001-1452); 29; 1686-169
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  • 10
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    Combined bearing and bypass loading on a graphite/epoxy laminate (1986)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: A combined experimental and analytical study was conducted to determine the behavior of a graphite/epoxy laminate subjected to combined bearing and bypass loading. Single-fastener quasi-isotropic specimens were loaded at various bearing-bypass ratios until damage was produced at the fastener hole. Damage-onset strengths and damage modes were then analyzed using local hole-boundary stresses calculated by a finite-element analysis. The tension data showed the expected linear interaction for combined bearing and bypass loading with damage developing in the net-section tension mode. However, the compression bearing-bypass strength showed an unexpected interaction involving the bearing mode.
    Keywords: STRUCTURAL MECHANICS
    Type: Composite Structures (ISSN 0263-8223); 6; 1-3,
    Format: text
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