Using OBR for pressure monitoring and BVID detection in type IV composite overwrapped pressure vessels

Type IV COPVs (Composite Overwrapped Pressure Vessels) are among the most suited structures for hydrogen storage. However, its complex modes of failure and requirement for periodic maintenance has led the industry to apply high safety factors on designs. This is one of the challenges inhibiting the widespread usage of the H₂ in commercial vehicles. Structural health monitoring based on optical fibers is an emerging technology that can overcome these problems, as a neural network of sensors can be integrated to the structure during manufacturing and is readily accessible over the vessel lifetime. This gives information about the real structure condition, reducing overall maintenance costs. Here, core optical fibers were embedded in type IV COPVs during the manufacturing process and monitored with OBR (Optical Backscatter Reflectometer). Sensors were interrogated during an impact detection test and a pressurization test until burst failure. Fibers were capable of detecting the position and intensity of the damage in the first test and provided strain profiles over the entire length of the vessel for longitudinal and circumferential directions on the second. Optical microscopy of vessel sections showed matrix accumulation around the optical fiber as the main cause of sensor’s failure. During pressurization, steep peaks of strain in the dome regions from the early measurements indicated the burst failure site.