Volume 7, Issue 1 (January 1979)

    Fracture Modes and Acoustic Emission of Composite Materials

    CODEN: JTEOAD

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    Abstract

    Unidirectional fibrous composite material laminae are the construction material of a laminate. Four failure modes can occur in this material, and the identification of these modes is as important as the identification of onset of fracture. Acoustic emission (AE) pulses, generated by the change in the stress field resulting from cracking in a material, have a unique pattern of amplitude distribution that depends only on the mode of fracture and the type of material. By using a tapered double-cantilever beam as grips for the unidirectional lamina, a crack with a constant stress intensity factor was induced, thus eliminating the factor of the stress level. Placing the lamina in different directions relative to the grips imposed a different failure mode. By plotting the log of the relative number of AE pulses above some level versus the log of the relative level, a single constant coefficient can be measured for each material and mode of fracture. The AE energy is proportional to the energy released by the cracking; this proportionality depends on the medium where the AE waves have to travel, and not on the cracking mode.


    Author Information:

    Rotem, A
    NASA-Ames Research Center, Materials and Physical Sciences Branch, Moffett Field, Calif.

    Altus, E
    NASA-Ames Research Center, Materials and Physical Sciences Branch, Moffett Field, Calif.


    Stock #: JTE11199J

    ISSN: 0090-3973

    DOI: 10.1520/JTE11199J

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    Author
    Title Fracture Modes and Acoustic Emission of Composite Materials
    Symposium , 0000-00-00
    Committee E07