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- Piezoresistive Sensing for Structural Health Monitoring in Liquid Hydrogen Tanks: A Study on Composite Cryotank TechnologiesPublication . Figueiredo, Matilde Rola; Pereira, João Pedro Nunes; Silva, Abílio Manuel Pereira daHydrogen has been emerging as a potential key energy carrier for sustainable aviation, yet its adoption is constrained by distinct engineering challenges, particularly its safe and lightweight storage. The present study investigates the feasibility of using the intrinsic piezoresistive properties of carbon-fibre reinforced prepreg composites, commonly employed in Type V cryogenic hydrogen tanks, for structural health monitoring. Given that matrix microcracking constitutes the predominant damage mechanism in these tanks and typically initiates at strain levels of 0.3%-0.5%, a preventive strain sensing approach was adopted based on these critical deformation thresholds. To achieve a proof of concept, 17-ply multidirectional carbon fibre/epoxy laminates based on Boeing’s cryotank from the Composite Cryotank Technologies and Demonstration program were produced and tested in their as-fabricated state and after controlled cryogenic cycling through five and ten cycles of immersion in liquid nitrogen (-196 ?) followed by reheating (52 ?). Unconditioned specimens showed a clear and repeatable piezoresistive response from surface measurements, with gauge factors ranging from -11.02 to -12.70, confirming their intrinsic self-sensing capability. Cryogenically cycled specimens exhibited moderate mechanical degradation and increased baseline electrical resistance, yet retained self-sensing performance, with gauge factor increases exceeding 85%. While volume (edge-to-edge) measurements were inconclusive, the consistent surface response demonstrates that unmodified carbon fibre/epoxy prepreg composites employed in Type V cryotanks can retain effective strain sensing functionality after cryogenic exposure and cycling, providing insights for the development of integrated structural health monitoring strategies in hydrogen storage applications.