STP907

    Response of Thick, Notched Laminates Subjected to Tension-Compression Cyclic Loads

    Published: Jan 1986


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    Abstract

    The fatigue response of a [(0/45/90/ −45)s]4 T300-5208 graphite/epoxy laminate with a drilled center hole subjected to constant-amplitude, fully reversed tension-compression loading was investigated. Damage evaluation techniques such as stiffness monitoring, penetrant-enhanced X-ray radiography, C-scan, laminate deply, and residual strength were used to establish the mechanisms of damage development as well as the relations between this damage and the stiffness, strength, and life of the laminate. Two load levels provided for fatigue lives of 105 to 106 cycles and significant stiffness reductions. Damage initiated at the hole as matrix cracking parallel to the fibers in all plies. Matrix cracks had a significant effect on delamination initiation and growth. Delaminations initiated near the surface in the densely cracked region at the hole and grew along major matrix cracks. Delaminations of smaller extent developed later throughout the interior of the laminate and followed similar growth patterns as those closer to the surface. Compressive properties degraded more rapidly than tensile properties. At the stress levels used in this investigation, residual tensile strength increased early in the fatigue life and remained approximately constant to near the end of life, when failure was precipitated by excessive laminate instability during the compressive portion of the loading.

    Keywords:

    composite materials, graphite/epoxy, fatigue, damage, delamination, strength, stiffness, life, nondestructive evaluation, notched laminate, tension, compression


    Author Information:

    Bakis, CE
    Graduate research assistant and professor, Virginia Polytechnic Institute and State University, Blacksburg, VA

    Stinchcomb, WW
    Graduate research assistant and professor, Virginia Polytechnic Institute and State University, Blacksburg, VA


    Paper ID: STP19993S

    Committee/Subcommittee: D30.04

    DOI: 10.1520/STP19993S


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