Dynamic Mechanical Behaviors and Microstructural Reaction Mechanisms of Graphene Oxide and Nano-SiO2–Reinforced Lunar Regolith Simulant Geopolymer under Impact Loading

Abstract It is essential that the establishment of future lunar bases depends entirely on the exploitation of local resources for all surface construction activities. Lunar regolith, as the main material resource, has the potential to prepare cementitious materials and be used for construction. In this study, using lunar regolith simulant as the raw material, graphene oxide (GO) and nano- SiO 2 (NS) with different mass fractions (GO: 0.04%–0.12%; NS: 0.5%–1.5%) were incorporated into the lunar regolith simulant geopolymer via ultrasonic dispersion to prepare the lunar regolith simulant geopolymer nanocomposite (LRSGN). To evaluate the dynamic performance of LRSGN cured in simulated lunar high-temperature environments, split Hopkinson pressure bar tests were conducted for compression and splitting tension. The resulting mechanical behavior and energy dissipation were examined, and microstructural changes were analyzed using scanning electron microscopy and thermogravimetry-derivative thermogravimetry. The experimental results display that the incorporation of GO and NS under impact loading significantly enhances the dynamic mechanical properties of LRSGN, the optimal mass fractions of GO and NS relative to the lunar regolith simulant are 0.08% and 1%, respectively. At an impact compression velocity of 6.7 m / s , the 28 day cured specimens with 0.08% GO and 1% NS achieved dynamic compressive strengths of 49.39 and 56.35 MPa, representing increases of 21.86% and 39.53% over the control group, respectively; at an impact splitting tensile velocity of 4.1 m / s , the dynamic splitting tensile strengths reached 17.77 and 22.46 MPa, corresponding to increases of 91.48% and 142.03%, respectively. GO and NS significantly improve the strain rate effect of LRSGN during dynamic splitting tensile processes, exhibiting distinct brittle fracture failure characteristics. NS demonstrates a superior mitigating effect on the dynamic failure extent of specimens compared to GO. Meanwhile, dissipated energy and energy dissipation efficiency first increase and then decrease with increasing GO and NS content, while they increase with rising impact velocity. The microstructure results show that GO and NS have filling, nucleation, size, and bridging effects, which contribute to the polymerization reaction in the system and better the original pore characteristics, thus improving the dynamic strength of the samples. However, once the GO and NS dosages surpass 0.08% and 1%, respectively, the excessive nanomaterials agglomerate adversely affecting the strength development of LRSGN. The research outcomes provide a significant experimental reference and theoretical basis for the selection of lunar-based engineering materials and structural design.