Mechanistic model for fiber crack density prediction in cyclically loaded carbon fiber-reinforced polymer during the damage initiation phase

Prediction of the fiber crack density (as one of the microstructural damages) for unidirectional fiber-reinforced polymer composite under monotonic tensile load, using strength models, has been reported in the literature. However, the microstructural damage prediction for a fiber-reinforced polymer subjected to fatigue loading is still a challenge. In this work, a progressive damage initiation model was developed to predict the fiber crack density in carbon fiber-reinforced polymer composite subjected to fatigue loading. A stochastic model was used for modeling the fiber fatigue strength. Reduction in effective life of the fiber was modeled using linear Miner's rule. Effect of fatigue strength parameters on fiber crack density was found to be considerable compared to the effect of interface shear strength. At a low number of cycles, fiber crack density obtained from the model was in good agreement with the experimentally measured fiber crack density.