Modeling of failure due to freezing of moisture and freeze-thaw cycling in composite materials

Based on Eshelby's elastic inclusion model, an analytical model is developed for predicting cracking induced by volumetric expansion in orthotropic composite materials due to freezing of trapped moisture in a slender rectangular flaw region. Conformal transformation and complex function method are used to obtain stress distribution in the matrix at the interior boundary. The stress field in the rectangular inclusion is derived by solving for two important variables characterising the expanded equilibrium boundary determined by the principle of minimum strain energy. For this specific case, the analytical model predicts a crack driving force that far exceeds the fracture toughness of the material at that temperature. The model prediction is verified by comparison with actual test data. Besides predicting static fracture, it is demonstrated how the model can be adapted to predict fatigue life of composites under freeze-thaw conditions.