Evaluation of transverse crack initiation in cross-ply CFRP laminates under fatigue loading

In this study, transverse crack initiation in cross-ply CFRP laminates under fatigue loading was evaluated focusing on the transverse crack growth and saturation. The number of cycles that a transverse crack initiates was predicted by the analytical model on the basis of the modified Paris law. In addition, the lower threshold of the transverse crack formation was researched by a modified Paris-law, and the fatigue limit of the transverse crack initiation was evaluated by calculating the stress applied in 90° layer where the increase of the transverse cracks was saturated. Moreover, transverse crack was observed by using scanning electron microscope (SEM) in order to investigate the mechanism of transverse crack initiation. As the results, the analytical results for predicting the transverse crack initiation showed good agreement with the experimental results. Moreover, it was shown that the lower threshold of the transverse crack formation existed, and that the stress applied in 90° layer at saturation state was almost equivalent to the fatigue limit of the transverse crack initiation from the experimental results. From the observation with SEM, it was found that the initiation of the transverse crack under fatigue loading depended on the interface property between fiber and matrix.