Simulation of delamination in composite materials under static and fatigue loading by cohesive zone models

This thesis is a dissertation focusing on the mechanics of delamination in laminated composites. Delamination, one of the most critical forms of failure in composite materials, may occur as a result of many causes and different types of loading, such as, for example, static or cyclic loading. This work presents an examination of the potential of cohesive interface elements for the prediction of delamination propagation under quasi-static mode I, mode II and mixed mode (I and II) loading, by a comparison between experimental tests and parametric analyses in order to evaluate the sensitivity of the elements to some parameters. The results of the comparison show that a rather good accordance may be obtained between experimental data and numerical simulations with a proper choice of the main model parameters. Moreover, a simplified mathematical model for the study of fatigue driven delamination is described. This model is particularly useful for investigating the performance of various formulations of interface elements that are used to simulate delamination under cyclic loading, because of its simplicity and efficiency that allow evaluating a large number of sets of parameter values. The model has been studied with different static constitutive laws and damage definitions, coupled with a particular fatigue degradation strategy. In particular, the sensitivity of the model, with the different proposed constitutive laws, has been evaluated with respect to some its key parameters.