Prediction of fatigue crack initiation in UD laminates under different stress ratios

Abstract In this chapter, a criterion for the prediction of fatigue crack initiation in UD composite plies for all R-ratios is proposed. First, a general background of the framework is given. This is followed by an overview of existing models for fatigue crack initiation prediction. The successful attributes of the discussed models are combined into one coherent criterion which succeeds in predicting crack initiation excellently for glass/epoxy, good for carbon/epoxy, and reasonable for carbon/PEEK. Lastly, several paths for future developments and expansion of the criterion are discussed.