STP696

    Ultrasonic Techniques for Inspecting Flat and Cylindrical Composite Specimens

    Published: Dec 1979


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    Abstract

    Ultrasonic techniques are discussed for inspection and evaluation of flat and cylindrical composite specimens. Immersion ultrasonic techniques are described using a 5-MHz broad-band focused transducer in the pulse-echo mode. Two types of recording methods are employed, conventional pen-lift C-scanning and analog scanning, augmented with photographs of oscilloscope traces of the pulse at selected locations. The complete scanning system is described, including a fixture for scanning tubular specimens. The techniques discussed are applied to monitoring flaw growth in graphite/epoxy coupons of [(0/±45/90)s]2 and [02/±45])2s layups with four types of initial flaws subjected to fully reversed spectrum fatigue loading. The flaws investigated are (1) circular hole, (2) embedded film patch, (3) internal ply gap, and (4) surface scratches. It was found that, in general, flaw growth is greater in specimens of [(0/±45/90)s]2 layup than in those of [(022/±45)2s layup. The residual tensile strengths for the preceding specimens, determined after four lifetimes of fatigue testing, are not significantly lower than the initial strengths.

    Keywords:

    nondestructive tests, ultrasonic scanning system, ultrasonic inspection techniques, ultrasonic transducers, pulse-echo, C-scans, composite laminates, graphite/epoxy, flat coupons, cylindrical specimens, critical flaws, flaw growth, spectrum fatigue testing, composite materials


    Author Information:

    Liber, T
    Senior research engineer, science advisor, and assistant research engineer, IIT Research Institute, Chicago, Ill

    Daniel, IM
    Senior research engineer, science advisor, and assistant research engineer, IIT Research Institute, Chicago, Ill

    Schramm, SW
    Senior research engineer, science advisor, and assistant research engineer, IIT Research Institute, Chicago, Ill


    Paper ID: STP36021S

    Committee/Subcommittee: D30.04

    DOI: 10.1520/STP36021S


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