STP1203: Failure Analysis of Aramid Fiber Reinforced Aluminum Laminates with Surface and Through Thickness Fatigue Cracks

    Macheret, Y
    Staff Engineer, Technical Consultant, Technical Specialist, and Technologist, Alcoa Technical Center, Alcoa Center, PA

    Bucci, RJ
    Staff Engineer, Technical Consultant, Technical Specialist, and Technologist, Alcoa Technical Center, Alcoa Center, PA

    Nordmark, GE
    Staff Engineer, Technical Consultant, Technical Specialist, and Technologist, Alcoa Technical Center, Alcoa Center, PA

    Kipp, TR
    Staff Engineer, Technical Consultant, Technical Specialist, and Technologist, Alcoa Technical Center, Alcoa Center, PA

    Pages: 17    Published: Jan 1993


    Abstract

    Fiber reinforced aluminum laminates are able to retard fatigue crack growth by transfer of load from cracked aluminum layers to intact fibers. The resulting crack bridging effect leads to superior laminate fatigue crack growth response compared to that of monolithic aluminum. In real laminate structures, fatigue cracks emanating from an open hole, as well as surface cracks initiated in an outer laminate aluminum layer, can be present. In this investigation, fatigue crack growth data on surface notch and open hole (through thickness notch) initiated fatigue cracks are presented. The failure analysis reveals that the surface initiated cracks propagate only in the outer aluminum layer, with fibers remaining intact. The open hole initiated cracks, on the other hand, propagate through the laminate thickness in all aluminum layers. In this case, depending on the laminate residual stress state (controlled by a post stretch procedure), a complete fiber failure may occur. When the fiber integrity is preserved, however, the laminates fatigue response in all cases is superior to that of monolithic aluminum.

    Keywords:

    laminates, fatigue, crack growth, failure analysis, aramid fibers, residual stress state, fiber failure


    Paper ID: STP14905S

    Committee/Subcommittee: D30.04

    DOI: 10.1520/STP14905S


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