Our understanding of the effects of damage on the performance of composite structures is far from complete. The complexity of the phenomena requires very detailed analytical models across many length scales supported by targeted tests that identify how damage is created and evolves and how larger scale properties such as stiffness and strength are affected. A lot of progress has been made in this direction but the numerical simulations that accompany the more advanced analysis models are not yet in a state where they can be applied to composite structures during design and preliminary analysis stages. To fill the need for analysis tools that can give reasonably accurate predictions and can be used in an optimisation environment, this book presented some candidate approaches for dealing with different types of damage in composite structures. As such, the methods have their limitations both in accuracy and range of applicability. Nevertheless, the material presented identified some basic trends and characteristics that can serve as useful design guidelines. They are summarised below. It is important to note that these guidelines are not absolute and may contradict each other in different situations. Still, they are very effective in narrowing down the field of options and selecting a robust design.