Novel modification strategy via GO and polyurethane for epoxy nanocomposites: Simultaneous enhancements of fracture toughness and liquid oxygen compatibility for cryotank applications

[Display omitted] •Rigid-and-soft filler modification strategy for epoxy nanocomposites.•GO could form a favorable interfacial bond with the epoxy resin matrix.•Fracture toughness values are enhanced by 207.26 % at room temperature and 243.02 % at 90 K.•No sensitivity phenomenon occurs during the liquid oxygen impact test. Fracture toughness and liquid oxygen (LOX) compatibility of epoxy nanocomposites for liquid oxygen composite cryotank applications are two main concerns. In this work, a novel rigid-and-soft hybrid-microstructure modification strategy is proposed to improve these two properties simultaneously. Graphene oxide (GO) nanosheets are physically incorporated, and polyurethane (PU) particles are formed through phase-separation process. When 10 parts of PU and 0.1 parts of GO are added into 100 parts of epoxy (i.e., 10 phr PU and 0.1 phr GO), the fracture toughness is enhanced by 207.26 % at room temperature and 243.02 % at 90 K, respectively. Meanwhile, no sensitivity phenomena such as explosion, burning, flash, or charring for the nanocomposite are observed during liquid oxygen impact testing. Consequently, experimental characterizations and multiscale finite element models are utilized to reveal the synergistic effects of GO and PU on fracture behaviors and impact energy absorption.