Performance evaluation of GNP-modified epoxy/carbon fiber composites after cryogenic thermal cycling for hydrogen storage applications

Carbon fibre-reinforced polymer (CFRP) composites are widely used in hydrogen storage systems due to their high strength-to-weight ratio and durability. However, repeated cryogenic thermal cycling, as experienced in hydrogen fuel applications, can induce thermal stresses that lead to microcracking, matrix-fibre debonding, and reduced mechanical performance. This study investigates the influence of graphene nanoplatelets (GNPs) on enhancing the cryogenic durability of CFRPs. GNPs were incorporated into the epoxy matrix at varying concentrations (0–0.75 wt%), and composites were subjected to controlled thermal cycling between −196 °C and 60 °C. Short-beam strength testing assessed mechanical performance, while scanning electron microscopy (SEM) and Raman mapping examined microstructural damage and dispersion. Results showed that, compared to unmodified CFRP, the incorporation of 0.1 wt% and 0.25 wt% GNPs increased strength by approximately 9 % and 10 %, respectively, before cycling, and by up to 20 % after 25 cycles. Strength reductions due to cycling were limited to 4.9 % and 5.7 % for the GNP-modified composites, compared to a 13.3 % loss observed in the unmodified composites. In contrast, 0.75 wt% GNPs led to agglomeration, increased cracking, and lower performance. SEM confirmed fewer cracks and improved interfacial adhesion at optimal GNP concentrations. These findings demonstrate that well-dispersed GNPs significantly enhance the mechanical resilience of CFRPs under cryogenic cycling, making them promising for hydrogen storage applications.