In recent years, the use of woven fabric composite materials has been increased due to their superior mechanical performance and low weight. Unit cell finite element modeling of these materials at meso level has proven to be an efficient method to predict their effective mechanical properties and reduce the need for extensive experiments. However, benchmark experiments reveal non-repeatability of test data at macro level which can be related to the uncertainties underlying fabric structure at meso level. This suggests that ideal unit cells of woven fabrics may be incapable of predicting macro-level properties accurately. The goal of this book is to discuss the effect of common meso-level uncertainties on the mechanical response of fabrics. A particular finite element method capable of capturing complex behaviour of fiber yarns is first studied. Next, it is shown how the method can be used along with full factorial statistical analysis methods to capture the main and interaction effects of both fabric geometrical factors and constitutive model parameters on the response of the material.