b'Embedded fiber optic sensorsNovel manufacturing technique that integrates optical sensors for real-time in situ sensinginto high-temperature high-strength materials advances in extreme environments development of smart sensors for harsh environments.S uccessful deployment of micro nuclear systems and many other systems requires monitoring capabilities to examine the status of these systems during operation. Fiber optic sensors have gained significant interest for structural health monitoring due to their distributed sensing capabilities, robust functionality in extreme environments, lightweight, and small size. Previous endeavors in using additive manufacturing processes to embed fiber optic sensors in PROJECT NUMBER:structural materials reported many challenges including defects between embedded 22P1074-015FP sensors and matrix as well as loss of sensor functionality after encapsulation. TOTAL APPROVED AMOUNT:This research developed an advanced manufacturing technology that embeds $125,000 over 1 year fiber optic sensors in high-temperature high-strength structural materials. A PRINCIPAL INVESTIGATOR:novel technique based on EFAS was developed and successfully demonstrated Xinchang Zhang to encapsulate optical fibers in stainless steel 316L. The result showed that good sensor functionality was obtained, as evidenced by limited optical attenuation of CO-INVESTIGATORS: the sensors after embedment compared to the as-received sensors. The sintering Jorgen Rufner, INL parameters affected optical attenuation of the fiber. High temperature, pressure, Zilong Hua, INL and hold time during EFAS enhanced sample density but adversely affected the optical transmission. The bonding condition between the embedded fibers and matrix fabricated at different conditions was studied by x-ray computed tomography and scanning electron microscopy. It was observed that a good bond was formed at the fiber-matrix interface with micro-sized material interdiffusion across the interface. A good fiber/matrix bond is critical to ensure strain coupling during strain measurement. Microstructure characterization revealed (0001) crystal orientation of the embedded fiber, which suggests the combined multi-physical fields during EFAS have no effects on the crystal orientation of the fiber after encapsulation. Mechanical properties of the materials were studied. Tensile testing confirmed the superior tensile strength and ductility of the matrix made at optimized conditions. Furthermore, the materials exhibited limited strength reduction (~70 MPa) upon the integration of sensors. These results show that optical fibers were successfully encapsulated in highly densified (98% relative density) stainless steel components under optimized fabrication conditions. The demonstrated effectiveness of using EFAS for fiber-matrix integration will greatly advance the development of smart sensing materials.108'