A multiplicative damage model for strength of fibrous compositematerials

摘要

Knowledge of the tensile strength properties of a fibrousncomposite material is essential in the design of reliable structuresnfrom that material. Determination of statistical models for the tensilenstrength of a composite material which provide good fits to experimentalndata from tensile tests on material specimens is therefore important fornengineering design. Perhaps the most commonly used statistical model isnthe Weibull distribution, based on `weakest link of a chain' arguments.nHowever, in many cases the usual Weibull distribution does notnadequately fit experimental data on tensile strength for compositenmaterials made from brittle fibers such as carbon. Here, an alternativenmodel is developed for tensile strength of carbon composites, which isnbased on a multiplicative cumulative-damage approach. This approachnresults in a 3-parameter extension of the Birnbaum-Saunders fatiguenmodel and incorporates the material specimen size (size effect) as anknown variable. This new distribution can also be written as an inversenGaussian-type distribution, which can be interpreted as the firstnpassage of the accumulated damage past a damage threshold, resulting innmaterial failure. The new model fits experimental tensile-strength data,nfor carbon micro-composites better than existing models, providing morenaccurate estimates of material strength