Composite sandwich structures: Damage detection and assessment using ultrasonic guided waves

Composite sandwich structures have emerged as versatile materials that leverage creative material combinations to enhance performance in aerospace, automotive, marine, and construction applications. Despite their coveted stiffness-to-weight and strength-to-weight characteristics, these structures are prone to a multitude of defects, either incurred during manufacturing or operation, that may lead to catastrophic failures of the systems in which they are used. This chapter thus highlights the various nondestructive inspection and structural health monitoring (SHM) methods that can assess the health of the structural systems, with a specific focus on composite sandwich structures, and hence prevent fatal failures. The focus herein centers on sensing and instrumentation techniques, state-of-the-art algorithms for data/image processing, and their interfaces by examining the recent developments in these fields, particularly in that of ultrasonic guided wave evaluation. A practical case study is demonstrated by showcasing a basic design of a sensor network and some results to localize defects. The chapter concludes with some insights into the developments needed to expand damage detection of sandwich structures from laboratory settings to commercially viable SHM systems.