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  • Other Sources  (8)
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  • 1
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    Environmental effects on defect growth in composite materials (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Data for evaluating the effects of moisture and temperature on the integrity of fiber composite components was gathered. In particular, the static and cyclic performance of three composite laminates containing flaws was investigated at room temperature and at 422 K (300 F) in wet and dry conditions.
    Keywords: COMPOSITE MATERIALS
    Type: NASA-CR-165213 , NAS 1.26:165213
    Format: application/pdf
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  • 2
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    Fatigue-crack-propagation and fracture- toughness characteristics of 7079 aluminum- alloy sheets and plates in three aged conditions (1968)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Fatigue crack propagation and fracture toughness characteristics of 7079 aluminum alloys in underage, peak age, and overaged conditions
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-CR-996
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  • 3
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    Effect of preload on the fatigue and static strength of composite laminates with defects (1977)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: The effect of a preload cycle on the structural performance of three graphite/epoxy composite laminates was studied. The layups studied were a laminate typical of general purpose structures (L1), a laminate representative of a filament wound tank (L2), and a laminate representative of turboengine fan blades. The effects of three sizes of simulated initial defects were studied. The tests developed static strength data, fatigue to failure data, and residual static data after application of a predetermined number of fatigue cycles. For L1 specimens, there was a slight trend for the static strength to be greater for preloaded specimens. After application of cyclic loading, however, the influence of preloading was insignificant. In L2 and L3 specimens there was no consistent difference in the static or fatigue results between preloaded and nonpreloaded specimens.
    Keywords: COMPOSITE MATERIALS
    Type: Annual Meeting on Recent advances in engineering science; Nov 14, 1977 - Nov 16, 1977; Bethlehem, PA
    Format: text
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  • 4
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    Evaluation of flawed composite structure under static and cyclic loading (1977)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: This paper presents the results of a program investigating the effects of initial defects on the fatigue and fracture response of composite laminates. The structural laminates investigated were a typical angle-ply laminate, a polar/hoop-wound pressure vessel laminate, and a typical engine fan blade laminate. Defects investigated were full- and half-penetration circular holes, full- and half-penetration slits, and countersink holes. Results are presented showing the effects of the defect size and type on the static fracture strength, fatigue performance, and residual static strength. The results of inspection procedures are shown, describing the effect of cyclic and static loadings on damage propagation in composite laminates. The data in this study were used to define proof test levels as a qualification procedure in composite structure subjected to cyclic loading.
    Keywords: COMPOSITE MATERIALS
    Type: Symposium on Fatigue of filamentary composite materials; Nov 15, 1976 - Nov 16, 1976; Denver, CO
    Format: text
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  • 5
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    Evaluation of flawed composite structural components under static and cyclic loading (1979)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The effects of initial defects on the fatigue and fracture response of graphite-epoxy composite laminates are presented. The structural laminates investigated were a typical angle ply laminate, a polar/hoop wound pressure vessel laminate, and a typical engine fan blade laminate. Defects investigated were full and half penetration circular holes, full and half penetration slits, and countersink holes. The effects of the defect size and type on the static fracture strength, fatigue performance, and residual static strength are shown as well as the results of loadings on damage propagation in composite laminates. The data obtained were used to define proof test levels as a qualification procedure in composite structure subjected to cyclic loading.
    Keywords: COMPOSITE MATERIALS
    Type: NASA-CR-135403
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  • 6
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    Environmental effects on composite fracture behavior (1981)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: An experimental program was carried out to investigate the effects of temperature and moisture on the damage development and fracture response of graphite/epoxy composites. Fracture response data were obtained for 20-ply laminates of different layup patterns for both room temperature and immediately after the application of a temperature transient causing the specimen to attain 150 C. It is found that elevated temperature degrades the notched strength of some laminates while not degrading others. The unnotched strength of all laminates tested at elevated temperatures was degraded. The effect of preloading on damage growth and moisture absorption, the effect of autoclave pressure during the laminate cure on fracture, and the variation of interlaminar shear properties with layup, moisture exposure, laminate material, and cure pressure are also discussed.
    Keywords: COMPOSITE MATERIALS
    Type: Symposium on Test methods and design allowables for fibrous composites; Oct 02, 1979 - Oct 03, 1979; Dearborn, MI
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  • 7
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    Compression and compression fatigue testing of composite laminates (1982)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The effects of moisture and temperature on the fatigue and fracture response of composite laminates under compression loads were investigated. The structural laminates studied were an intermediate stiffness graphite-epoxy composite (a typical angle ply laimna liminate had a typical fan blade laminate). Full and half penetration slits and impact delaminations were the defects examined. Results are presented which show the effects of moisture on the fracture and fatigue strength at room temperature, 394 K (250 F), and 422 K (300 F). Static tests results show the effects of defect size and type on the compression-fracture strength under moisture and thermal environments. The cyclic tests results compare the fatigue lives and residual compression strength under compression only and under tension-compression fatigue loading.
    Keywords: COMPOSITE MATERIALS
    Type: NASA-CR-168023 , NAS 1.26:168023 , D180-27619-1
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  • 8
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    Valsalva's maneuver revisited: a quantitative method yielding insights into human autonomic control (1996)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Seventeen healthy supine subjects performed graded Valsalva maneuvers. In four subjects, transesophageal echographic aortic cross-sectional areas decreased during and increased after straining. During the first seconds of straining, when aortic cross-sectional area was declining and peripheral arterial pressure was rising, peroneal sympathetic muscle neurons were nearly silent. Then, as aortic cross-sectional area and peripheral pressure both declined, sympathetic muscle nerve activity increased, in proportion to the intensity of straining. Poststraining arterial pressure elevations were proportional to preceding increases of sympathetic activity. Sympathetic inhibition after straining persisted much longer than arterial and right atrial pressure elevations. Similarly, R-R intervals changed in parallel with peripheral arterial pressure, until approximately 45 s after the onset of straining, when R-R intervals were greater and arterial pressures were smaller than prestraining levels. Our conclusions are as follows: opposing changes of carotid and aortic baroreceptor inputs reduce sympathetic muscle and increase vagal cardiac motor neuronal firing; parallel changes of barorsensory inputs provoke reciprocal changes of sympathetic and direct changes of vagal firing; and pressure transients lasting only seconds reset arterial pressure-sympathetic and -vagal response relations.
    Keywords: Aerospace Medicine
    Type: The American journal of physiology (ISSN 0002-9513); 271; 3 Pt 2; H1240-9
    Format: text
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