STP580

    Application of a Special X-Ray Nondestructive Testing Technique for Monitoring Damage Zone Growth in Composite Laminates

    Published: Jan 1975


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    Abstract

    A modified X-ray nondestructive testing technique was used to study matrix cracks parallel to fibers and delaminations between plies in graphite-epoxy composite material. A tetrabromoethane (TBE) opaque additive applied at the source of the damage zones enhanced the flaw image.

    Center-slit specimens were fabricated from Modmor II/Narmco 5208 graphite-epoxy laminates with three different ply orientations. Tensile ramp and sawtooth cyclic loadings at different levels were applied to these specimens. Periodic X-ray monitoring was conducted to observe the initiation and growth of cracks and delaminations at the slit tips. The initiation of damage zones appeared as fiber separation in the ±45-deg directions tangent to the semicircular periphery of the cutout tips. As the load level was increased, this fiber separation continued while fiber separation at other locations also appeared.

    Delamination first occurred at approximately the same time as fiber separation. The delaminated area was found to surround the most severe fiber separation region and grew in size as the load level was increased.

    Limited test results indicated a slow and an accelerated damage growth rate during ramp loading. For cyclic loading the majority of growth occurred on the first load cycle. Subsequent cyclic loading to the same level contributed little additional growth in the majority cases.

    Keywords:

    composite materials, nondestructive tests, cracking (fracture), crack propagation, damage detection, tension tests, stress concentration, radiography, opaque additive, failure, fatigue


    Author Information:

    Chang, FH
    Senior research scientist, project research scientist, senior structures engineer, and group design engineer, General Dynamics, Fort Worth, Tex.

    Couchman, JC
    Senior research scientist, project research scientist, senior structures engineer, and group design engineer, General Dynamics, Fort Worth, Tex.

    Eisenmann, JR
    Senior research scientist, project research scientist, senior structures engineer, and group design engineer, General Dynamics, Fort Worth, Tex.

    Yee, BGW
    Senior research scientist, project research scientist, senior structures engineer, and group design engineer, General Dynamics, Fort Worth, Tex.


    Paper ID: STP32307S

    Committee/Subcommittee: D30.04

    DOI: 10.1520/STP32307S


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