Externally Bonded FBG Strain Sensors Structural Health Monitoring of Marine Hydrokinetic Structures

To reduce operations and maintenance costs, mitigate failures, and improve capacity factor, structural health‐monitoring systems can provide key information to improve management of marine hydrokinetic devices. While present systems include instrumentation to measure power output, few adequately monitor mechanical load and structural response, which are equally important for determining device performance and integrity. Fiber optic fiber Bragg grating (FBG) sensors could prove to be a reliable and unobtrusive measurement tool for marine power; however, externally adhered FBGs have not been extensively studied on submerged, dynamic structures. Thus investigations on thebBond integrity between sensor and structure of a kinetic system, FBG strain sensors were tested in dry and environmentally soaked conditions under both static and fatigue loads. Composite coupons were strained in a fatigue testing system and monitored. Dry results demonstrated very high correlation and response from the FBG sensors, up to coupon failure. The environmentally soaked samples and sensors were subject to many failure modes and verified the developer's recommendation to not externally adhere the FBG strain sensors without additional mechanical and environmental protections.