Abstract
Kinetic theories of crack growth have been used in the past to estimate the lifetimes of load-bearing polymeric materials. The theme is simple. Knowledge of the kinetic criterion involving stress-versus-crack velocity allows prediction of the time at which the crack reaches an unstable size, thereby causing failure of the structure. The present work shows some of the complications inherent in constant stress life-prediction methodology, specifically, the complications of using different theoretical results. These differences involve the following, both with respect to the governing creep functions: first, the forms of the arguments obtained from different kinetic theories and, second, the various forms for the power-law representation. Some further complications are discussed in relation to conditions wherein the material is in a continuously relaxing state rather than a full relaxed state under the time-constant history. Theoretical means are derived to overcome some of these difficulties. 1 figure, 1 table.
Published Version
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