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    A Model for Predicting Thermal and Elastic Constants of Wrinkled Regions in Composite Materials

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    Previous theoretical attempts to predict the mechanical behavior of curvedfiber composites have provided only upper or lower bound estimates of the elastic constants of orthotropic wrinkled regions. In this paper, a new model is described that extends the prior work in the following ways: (1) for a certain class of wrinkles the approach is exact in that stress equilibrium and strain compatibility are simultaneously satisfied; (2) the model can treat wrinkled regions that are non-orthotropic because of asymmetries in the wrinkle's waveform; and (3) the model explicitly provides results for all the elastic constants and the thermal expansion coefficients, of the (monoclinic) wrinkled region. For orthotropic wrinkled regions, a model also is provided for thermal conductivities. The approach is appropriate to wrinkles formed by “cooperative” distortions of reinforcement layers, in which the waveform of each layer is (more or less) in phase with the waveforms of the other layers. Implementation of the analysis is numerical, using a simple specialized finite-element formulation. Examples of the model's predictions are compared to predictions of previous analyses.


    composite materials, defects, elastic properties, fiber composites, laminates, stress analysis, thermal conductivity, thermal expansion, waves, wrinkles, fatigue (materials), fracture mechanics

    Author Information:

    Jortner, J
    Research engineer, Jortner Research & Engineering, Inc., Costa Mesa, Calif.

    Committee/Subcommittee: E08.01

    DOI: 10.1520/STP30206S