Static and fatigue behaviors of epoxy-based sealing layers for underground hydrogen energy storage

Underground hydrogen energy storage (UHES) in lined rock caverns (LRCs) presents a highly promising and innovative remedy to mitigate the inherent volatility of renewable energy sources. However, this approach necessitates a reliable sealing layer with enhanced mechanical properties to ensure stability and security. In this study, a novel composite sealing layer is fabricated by employing the epoxy (EP) as matrix and incorporating graphene oxide (GO) and aluminum oxide (AO) as nanofillers. The static behaviors of the sealing layers are evaluated combined with the digital image correlation (DIC) system and scanning electron microscope (SEM) under coupled temperature loading, while the fatigue behaviors are tested at various stress amplitudes and temperature environment. With the rise in temperature, the molecular thermal motion of EP becomes more pronounced, which reduce both the elastic modulus (E) and ultimate strength (sigma(ult)) of the composite sealing layers. However, the ultimate displacement (s(ult)) increases with increasing temperature, which can be attributed to the softening of the EP matrix and the enhanced debonded and bridging effect of nanofillers. As the mass fraction (M-f) of nanofillers increases, the magnitude of the increase in the maximum values of strain range (epsilon(ran)) diminishes, which can be attributed to the incorporation of nanofillers facilitate the absorption and dispersion of internal energy within the composite materials. The optimized composite sealing layer with 10% Mf of binary nanofillers demonstrated s(ult) values of 28.54 mmm, 30.16 mm and 33.57 mm at room temperature, 50 C-degrees and 100 C-degrees, respectively, which represent a 32.77%, 38.03% and 46.21% increase compared to pure EP. Besides, the maximum value of epsilon(ran) when the upper fatigue stress is 0.7 sigma(ult) is increased to 2.55 x 10(-3). The findings presented in this study contribute to the improvement of safety and durability of UHES in LRCs.