The purpose of this research project is to implement cohesive zone modelling in the finite element analysis of composite structures subjected to fatigue loading. The focus of the research lies in the simulation of delamination growth when an initial delamination is present. Delamination is a common failure mode in composite structures. It can be the result of a number of different things such as impact damage, manufacturing defects, fatigue loading or out-of-plane loading, for example when the structure buckles. The characterisation of the delamination growth behaviour is important to ensure safe design. Simulations are a vital part to this characterisation to decrease the necessity of experimental tests, which are often time-consuming and expensive.