STP775

    Stiffness-Reduction Mechanisms in Composite Laminates

    Published: Jan 1982


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    Abstract

    It now is recognized widely that stiffness changes during the service loading of composite laminates can be significantly large, especially as those changes affect deflections, dimensional changes, vibration characteristics, and load or stress distributions. Several generic sources of stiffness change can be identified, in various degrees, in fibrous composite materials. The source which occurs quite early in the life of a specimen or component is matrix cracking, the subject of this paper. While most laboratories now report stiffness changes, very little systematic philosophy has been developed to account for and explain such stiffness changes. The complexity of this situation requires systematic study, and motivates the search for a model, or models, which can describe the behavior and predict unfamiliar response. The present paper reports the results of an experimental program and an analytical modelling exercise which indicate that much of the observed matrix cracking can be predicted and the effects on stiffness calculated with various degrees of accuracy depending upon the sophistication of the model used.

    Keywords:

    composite materials, stiffness, matrix (transverse) cracking, crack density, characteristic damage state (CDS), laminate


    Author Information:

    Highsmith, AL
    Graduate research assistant and professor, Virginia Polytechnic Institute and State University, Blacksburg, Va.

    Reifsnider, KL
    Graduate research assistant and professor, Virginia Polytechnic Institute and State University, Blacksburg, Va.


    Paper ID: STP34323S

    Committee/Subcommittee: E08.06

    DOI: 10.1520/STP34323S


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