Volume 4, Issue 4 (April 2007)

    Strength of Quasi-Isotropic Co-Cured Composite Joints Under Quasi-static and Fatigue Loading

    (Received 30 August 2006; accepted 19 March 2007)

    Published Online: 2007

    CODEN: JAIOAD

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    Abstract

    Three composite joint configurations, namely, the straight laminate (SL), the single lap, and the single nested overlap (SNO) joints are investigated to ascertain the improvement of the SNO joint over the single lap joint under quasi-static and cyclic loading. The SNO joint is a co-cured composite joint design proposed previously, while the SL represents a perfect joint and serves as an upper bound for static strength and fatigue life comparisons. Stress-number curves are generated based on constant amplitude tension-tension cyclic loading at a frequency of 5 Hz and stress ratio (R) of 0.1 for quasi-isotropic graphite/epoxy (IM7/8551-7) joints. The maximum fatigue load is varied between an average of 70-90 % UTS for SL, 20–80 % ultimate tensile strength (UTS) for single lap joints and 40–95 % UTS for SNO joints. Fatigue run-out is defined at 1×106 cycles. The fatigue strength improvement of SNO joint is ascertained quantitatively through two indicators. Three quasi-static acoustic emission (AE) count peaks were identified during monotonic loading before eventually reaching a maximum at ultimate failure. The cumulative AE count peaks are used as a collective measurement of the significant damage event incurred under specific loading and subsequently correlated to the fatigue performance of each of these three joint configurations.


    Author Information:

    Tan, Xinyuan
    Graduate Research Assistant, School of Aerospace Engineering, Georgia Institute of Technology,

    Armanios, Erian
    Professor, School of Aerospace Engineering, Georgia Institute of Technology,


    Stock #: JAI100776

    ISSN: 1546-962X

    DOI: 10.1520/JAI100776

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    Author
    Title Strength of Quasi-Isotropic Co-Cured Composite Joints Under Quasi-static and Fatigue Loading
    Symposium , 0000-00-00
    Committee D30