Microcrack Testing and Monitoring Using FBGS for Hydrogen Tanks

The transition toward zero-emission aviation demands the development of lightweight and safe storage systems for cryogenic hydrogen. Type V composite tanks, which lack a metallic or polymeric liner, offer significant advantages in terms of mass reduction and thermal compatibility. However, their longterm viability is challenged by hydrogen permeability due to matrix microcracking, which can occur under cryogenic conditions and compromise tank integrity. This study explores an indirect method to assess microcrack formation by measuring the thermal expansion behavior of a composite laminate. Using controlled thermal cycles and induced damage scenarios, changes in the coefficient of thermal expansion (CTE) were monitored and correlated with internal microcracking. Results demonstrate a measurable and repeatable variation in thermal expansion after damage, supporting its use as a structural health monitoring (SHM) indicator. The findings provide a promising path toward the implementation of non-destructive techniques for in-service integrity assessment of Type V hydrogen tanks.