Abstract: The future construction of the lunar base advocates the full use of the lunar material resources for the construction of the lunar surface. In this paper, graphene oxide (GO) and nano-SiO₂ (NS) were added to lunar regolith simulant geopolymer by ball milling and ultrasonic dispersion to prepare lunar regolith simulant geopolymer nanocomposites (LRSGN). The mechanical properties of LRSGN under high temperature curing environment of the moon were studied. The surface crack deformation and strain evolution distribution characteristics were analyzed by digital image correlation (DIC) technology. The microstructure evolution was characterized by X-ray diffraction(XRD), Fourier transform infrared spectrometer(FTIR), mercury intrusion porosimetry (MIP) and scanning electron microscope (SEM). The results show that the addition of GO and NS significantly improve the mechanical properties of LRSGN, and the optimum contents are 0.08% and 1%, respectively. The maximum compressive strength of the 28 d samples mixed with GO and NS in the lunar regolith simulant by ultrasonic dispersion were increased by 93% and 145%, the maximum splitting tensile strength were increased by123% and 219%, and the maximum flexural strength were increased by 64% and 144%, respectively, compared with the control group. The enhancement effect of mechanical properties is much better than that of ball milling dispersion. The proper incorporation of GO and NS will also delay the formation of local strain concentration zone of LRSGN. The maximum principal strain is at the crack of the sample surface and appears in the form of local strain concentration zone. The microstructure results show that GO and NS have nucleation effect, filling effect, size effect and bridging effect, which promote the polymerization reaction in the system and improve the original pore characteristics, thus improving the mechanical properties of the samples. However, with the increasing content of GO and NS, the agglomeration effect of nanomaterials will occur, which is not conducive to the development of LRSGN strength. These findings provide a theoretical basis and experimental data for material selection and structural design of lunar engineering.

Key words: lunar regolith simulant geopolymer, graphene oxide, nano-SiO2, mechanical properties, digital image correlation (DIC) technology, microstructure