A novel subcycle composite delamination growth model under fatigue cyclic loadings

A new subcycle-based delamination growth model is proposed. The key idea is to model delamination growth at any time instant within a cyclic loading, rather than the cycle-averaged growth kinetics. First, some existing models are briefly reviewed for the fatigue delamination growth analysis of composite materials. Following this, two hypotheses are given for the derivation of the subcycle delamination growth model: (1) delamination growth does not happen during the unloading path and (2) delamination growth does not happen when the applied loading is below a reference level during the loading path. Mathematical expression is given for the calculation of delamination growth rate. Next, the extension of the proposed model is discussed to use both stress intensity factor and energy release rate as the driving force parameters, which are widely used in the open literature. Finally, the model predictions are compared with extensive experimental data under different stress ratios for model validation. One of the advantages of the proposed model is that the stress ratio dependent delamination growth can be predicted. Some conclusions and future work are drawn based on the proposed method.