Fiber Bragg Grating (FBG) sensors measure deviation in a reflected wavelength of light to detect in-situ strain. These sensors are immune to electromagnetic interference, and the inclusion of multiple FBGs on the same fiber allows for a seamlessly integrated sensing network. FBGs are attractive for embedded sensing in aerospace applications due to their small noninvasive size and prospect of constant, real-time nondestructive evaluation. In this study, FBG sensors are embedded in aluminum 6061 via ultrasonic additive manufacturing (UAM), a rapid prototyping process that uses high power ultrasonic vibrations to weld similar and dissimilar metal foils together. UAM was chosen due to the desire to embed FBG sensors at low temperatures, a requirement that excludes other additive processes such as selective laser sintering or fusion deposition modeling. In this paper, the embedded FBGs are characterized in terms of birefringence losses, post embedding strain shifts, consolidation quality, and strain sensing performance. Sensors embedded into an ASTM test piece are compared against an exterior surface mounted foil strain gage at both room and elevated temperatures using cyclic tensile tests.
John J. Schomer, Adam J. Hehr, and Marcelo J. Dapino, "Characterization of embedded fiber optic strain sensors into metallic structures via ultrasonic additive manufacturing," Proc. SPIE 9803, Sensors and Smart Structures Technologies for Civil, Mechanical, and Aerospace Systems 2016, 980320 (Presented at SPIE Smart Structures and Materials + Nondestructive Evaluation and Health Monitoring: March 23, 2016; Published: 20 April 2016); https://doi.org/10.1117/12.2219690.
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