Effects of cyclic cryogenic aging on carbon fiber-reinforced polycarbonate composites for lightweight hydrogen storage aerospace applications

• 3D printing of FRP with different infill densities to characterize the importance of the air inclusion or printing defects on the material performance. • Development of aging protocols to simulate the cryogenic cycles of short-carbon fibre reinforced polycarbonate employed in liquid hydrogen environment • Three cycle durations and three number of cycles were performed employing a maximum of 150 days of tailored accelerated aging. • The duration and number of cycles dominate the degradation of PC + CF material, showing a synergistic effect. • Development of cracks has been assessed for different aging protocols. Hydrogen (H2) as future fuel for the transportation sector has gained significant attention in light of global efforts to reduce GreenΗouse Gas emissions. The deployment of hydrogen storage systems necessitates increased attention to the durability and longevity of the materials involved. Composite materials have shown promise for hydrogen storage due to their increased specific properties and corrosion resistance in aggressive environments. However, limited data exists regarding the long-term performance of polymer composites cyclic cryogenic exposure. This work investigates the material response of Fused Filament Fabricated Polycarbonate composites reinforced with short carbon fibers, after undergoing accelerated cryogenic cyclic aging in Liquid Nitrogen. To assess possible influence of manufacturing-related defects, printed specimens with two different infill densities were studied. The effects were evaluated in terms of mechanical and viscoelastic property changes, while inherent material characteristics and chemical changes were analyzed via X-ray Computed Tomography (XCT) and Infrared Spectroscopy scans. Mechanical degradation was observed, primarily due to the propagation of microcracks, which was more pronounced in the case of 25% infilled specimens as was highlighted by XCT scans. The degradation was attributed also to the mismatch in Coefficient of Thermal Expansion (CTE) values and the presence of air pockets within the printed material.