The applications of composite materials are on the rise in many engineering fields, including civil and aerospace structures. In the aerospace industry, for instance, manufacturers have increasingly moved toward replacing lightweight metals with composites for large areas of primary structure. The motivation for this migration stems from the industry’s need to improve the performance and the fuel efficiency of aircrafts that can be attained by reducing structural weight. These achievements are possible owing to the unique properties of composites that have been extensively discussed in the first part of this book. However, composite materials may be prone to different types of defects, including but not limited to fiber breaks, delaminations, and voids. Owing to the critical role that composites have in modern engineering, a great effort has been devoted by academia and industry to the development of reliable and robust tools for the nondestructive evaluation (NDE) and structural health monitoring (SHM) of such structural elements. In aeronautics, for instance, the increasing demand in lowering maintenance costs contributes to the growing development of SHM systems to ensure continuous knowledge of the structural state of the monitored aircraft components.