Predictive modeling of microcracking in carbon-fiber/epoxy composites at cryogenic temperatures

Authors

  • John F. Timmerman,

    1. Polymeric Composites Laboratory, Department of Chemical Engineering, University of Washington, Seattle, Washington 98195
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  • James C. Seferis

    Corresponding author
    1. Polymeric Composites Laboratory, Department of Chemical Engineering, University of Washington, Seattle, Washington 98195
    • Polymeric Composites Laboratory, Department of Chemical Engineering, University of Washington, Seattle, Washington 98195
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Abstract

The temperature at which microcracking occurred in symmetrical cross-ply carbon-fiber/epoxy composite materials was predicted with a yield-stress-based failure model. A fracture mechanics analysis of the in situ strength of the ply groups in a composite material was combined with a compound beam determination of thermal stress development to create the predictive model. This approach, unlike many other models, incorporated the change in the material properties with temperature with the room-temperature properties of the laminate to predict the low-temperature behavior of the ply groups. Dynamic mechanical analysis was used to assess microcracking at cryogenic temperatures through the observation of discontinuities in the material properties during failure. Four different material systems were studied, and the model accurately predicted the onset temperature for microcracking in three of the four cases. It was shown that the room-temperature properties of a fiber-reinforced polymeric composite laminate, appropriately modified to account for property variations at low temperatures, could be used to predict transverse microcracking as a response to thermal stresses at cryogenic temperatures. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1104–1110, 2004

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