STP787: Predicting Viscoelastic Response and Delayed Failures in General Laminated Composites

    Dillard, DA
    Assistant Professor, University of Missouri-Rolla, Rolla, Mo.

    Morris, DH
    Associate Professor and Professor, Virginia Polytechnic Institute and State University, Blacksburg, Va.

    Brinson, HF
    Associate Professor and Professor, Virginia Polytechnic Institute and State University, Blacksburg, Va.

    Pages: 14    Published: Jan 1982


    Abstract

    Although graphite fibers behave in an essentially clastic manner, the polymeric matrix of graphite/epoxy composites is a viscoelastic material which exhibits creep and delayed failures. The creep process is quite slow at room temperature, but may be accelerated by higher temperatures, moisture absorption, and other factors. Techniques are being studied to predict long-term behavior of general laminates based on short-term observations of the unidirectional material at elevated temperatures. A preliminary numerical procedure based on lamination theory is developed for predicting creep and delayed failures in laminated composites. A modification of the Findley nonlinear power law is used to model the constitutive behavior of a lamina. An adaptation of the Tsai-Hill failure criterion is used to predict the time-dependent strength of a lamina. Predicted creep and delayed failure results are compared with typical experimental data.

    Keywords:

    composite materials, graphite/epoxy, creep, delayed failures, viscoelasticity, lamination theory, accelerated characterization


    Paper ID: STP28490S

    Committee/Subcommittee: D30.04

    DOI: 10.1520/STP28490S


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