Influence of Polyurethane/Nano‐SiO₂ on the Cryogenic Peeling Resistance of Glass Fiber Reinforced Epoxy Matrix Composites

Epoxy resin (EP) adhesive performance is critical for the glass fiber‐reinforced composites (GFRP) in the Membrane‐Type liquefied natural gas (LNG) cargo containment systems (CCS). In this work, the polyurethane‐modified epoxy resin (EPU) and Nano‐SiO 2 were introduced into EP to develop a resin system with enhanced bonding strength and durability for bonding glass fiber and aluminum foil. The results demonstrated that the peel strength of the EP/EPU50/2 wt.% Nano‐SiO 2 ‐GF reached 3.78 kN m −1 at room temperature (RT), which was approximately 172% higher than that of EP‐GF (1.39 kN m −1 ). Even at −190°C, the peel strength remained 2.66 kN m −1 . The continuous flexible polyurethane phase dissipated mechanical energy through chain extension and hydrogen bonding, while the Nano‐SiO 2 improved the crack propagation resistance, thus enhancing adhesion. In addition, after 30 days of exposure to ultra‐low temperature (−196°C) and 40 thermal cycles, the peel strength of EP/EPU50/2 wt.% Nano‐SiO 2 ‐GF at RT still reached 2.92 kN m −1 and 3.53 kN m −1 , respectively. SEM analysis revealed that ultra‐low temperature could induce interfacial debonding between the resin layer and aluminum foil. The transition of failure mode from cohesive failure to adhesive failure was the main reason for the decrease in peel strength.