The effect of fiber bridging on mode I fatigue delamination propagation-Part II: Cohesive zone model

This is Part II of a series of two papers in which the effect of fiber bridging on fatigue delamination propagation is assessed. In Part I, unidirectional double cantilever beam specimens composed of the carbon fiber-reinforced polymer prepreg AS4/8552 were tested by means of fatigue cycling. Fiber bridging in beam specimens composed of unidirectional plies causes the apparent fatigue delamination curves to exhibit growth which is slower than that for the case when fiber bridging does not occur. Generally, fiber bridging does not occur in laminate structures. In Part II of this study, a cohesive zone model (CZM) is developed and used to carry out finite element analyses to simulate the experiments. The CZM is employed to quantify and eliminate the contribution of fiber bridging to the fatigue delamination growth curves. In this way, more realistic results are obtained. These results are compared to an upper bound curve determined in Part I. Effect of fiber bridging on fatigue delamination propagation is quantified. To this end, a cohesive zone model is developed. Fatigue delamination propagation tests were numerically simulated. Fiber bridging was seen to increase the fatigue fracture toughness by about 22%. image