Book excerpt: This book provides valuable information about fiber-reinforced polymer composites, with emphasis in the process of water absorption by experiments and simulation. In this monograph, we present and discuss emerging topics related to fundamentals, engineering applications, advanced mathematical modeling applied to Fickian and non-Fickian diffusion processes, analytical and computational procedures and experiments on water absorption of polymer composites reinforced by vegetable fibers. The book serves as a comprehensive learning tool for engineers, professionals, and researchers involved in this advanced interdisciplinary field, and as a reference work for both undergraduate and graduate courses.