Ultrasonic inspection detects hidden damage in composites

Laminated fiber-reinforced composite materials offer excellent durability and high strength- and stiffness-to-weight ratios. For this reason, they often provide superior performance to metals in both primary and secondary structural applications. However, polymer-matrix composites are susceptible to interlaminar delaminations, fiber fractures, matrix cracking, fiber/matrix debonding, and other damage that can degrade structural performance. Such damage can occur during manufacture, assembly, and/or normal service, and may have an influence on usage and repair decisions. Because of this potential for damage, it is important to be able to nondestructively inspect and characterize damage in fiber-reinforced materials. Ultrasonics represents a state-of-the-art technique for performing such inspections. Recent advances in transducers, instrumentation, and scanning hardware have increased the effectiveness of this method of detecting and characterizing flaws. These advances are discussed in this article.