2. Introduction to Nondestructive Testing and Evaluation of Fiber-Reinforced Composites

This chapter discussed the different approaches used for the evaluation of the health status of composite materials using nondestructive testing and evaluation (NDT&E) techniques. The discussion started with the terminology, proceeding to some general requirements of NDT in terms of performance, portability, and safety concerns. A description of the perception of defects and flaws vis-à-vis the different NDT techniques is also provided. A section was also devoted to personnel qualifications and certification as well as a brief introduction on the semantics of the most important formulations used in the NDT of composite materials. In the context of this book, NDT denotes a descriptive term used to indicate the examination of fiber-reinforced composite materials and components without changing or destroying their original attributes. Although the terms NDT and NDE are often used interchangeably in most of the literature (including some references in this chapter), these two terms are different and should be treated as such by the readers of this book consistent with the definitions outlined in the first section. Typical examples of the application of NDT are found in a number of fiber-reinforced composite structures including aircraft, spacecraft (i.e., space shuttle), motor vehicles, pipelines, bridge decks, refineries, buildings, and oil platforms which are all inspected using NDT. When used correctly, NDT can also serve as a Quality Assurance Management tool that can give impressive results, but this requires an understanding of the various methods available, their capabilities and limitations, as well as the knowledge of the relevant standards and specifications for performing the tests. In general, NDT can easily help identify materials, products, and equipment that fail to achieve their design requirements or projected life due to undetected defects and help schedule repair, maintenance, or replacement activities. NDT also helps engineers to mitigate unsafe conditions or catastrophic failure of composite structures, as well as the loss of revenue by providing an optimum window for timely planned repair and maintenance activities.