Spatial Strain Sensing Using Embedded Fiber Optics

Ultrasonic additive manufacturing, a three-dimensional metal printing technology, uses ultrasonic energy to produce metallurgical bonds between layers of metal foils near room temperature. This low-temperature attribute of the process enables integration of temperature-sensitive components, such as fiber optic strain sensors, directly into metal structures for load and health monitoring applications. In this study, a high-definition fiber optic strain sensor was embedded into an aluminum alloy, 6061-T6, bracket for fatigue testing. The fiber optic system allowed mapping of the strain along the length of the fiber with a spatial resolution near 1 mm, and the embedded fiber exhibited correlation with surface strains measured by digital image correlation. Finite element modeling was carried out to rationalize and compare the measured strain profile’s character and magnitude. After discussing these results, a future outlook on the technology and its applications is described.