Application of embedded metal-packaged FBG sensors for Internal monitoring of type III hydrogen storage vessels

Type III composite hydrogen storage vessels consist of a metallic liner wrapped with carbon fibers. During post-curing cooling, thermal expansion mismatch between layers induces residual strain, threatening structural integrity and safety. To enable real-time monitoring, this study embeds compact metal-packaged fiber Bragg grating (FBG) sensors inside the vessel. A distributed temperature–strain monitoring system was developed to track the full cooling process. The temperature sensors showed a sensitivity of 10.38 pm/°C within 150 °C, while the strain sensors exhibited 0.27 pm/με up to 10,000 με. Embedded sensors operated continuously for 24 hours with stable, distortion-free signals, confirming their reliability in high-temperature, high-strain composite environments.