Progressive Failure-Based Composite Durability Model

The proposed program builds on prior development, implementation and validation of models for progressive failure of monotonically loaded composite structures to derive a durability model for predicting fatigue lifetime of composite structures. The durability model incorporates a model for fatigue damage accumulation in composites based on a generalized Paris' Law, and a composite residual-strength model based on progressive failure analysis methods. Finite-element models will be used in conjunction with coupon-level laboratory tests to calibrate fatigue- and residual-strength models with respect to material characteristics and definition of local load-intensity (stress- or strain intensity) and damage-accumulation functions. Several candidate composite strength models will be evaluated analytically to determine the best predictors of load intensity and damage accumulation to match damage growth measured under cyclic loadings. The product of the Phase I effort will be a unified model for composite durability analysis. This model will be refined and applied to analyze results of actual component durability tests in Phase II as a means to speed industrial application of the model.