Constitutive model analysis of Chang'e-5 simulated lunar regolith solidified bodies under compression

China's Chang'e-5 spacecraft successfully collected 1731 g of Lunar regolith and returned it to Earth on December 17, 2020. In this paper, Chang'e-5 simulated Lunar regolith is used as the main material to form stable and dense solid Lunar soil structures by adding different amounts of an inorganic curing agent and water. The internal morphology, failure morphology under uniaxial compression, and stress–strain relationship of the Lunar regolith solidified samples (L-R-S-Ss) are then investigated. The damage constitutive model of the Lunar regolith cured body is analyzed according to the stress–strain curves, with the following results found. (1) Scanning electron microscopy indicates that the L-R-S-Ss contain more microvoids and microfractures, which are the main factors that lead to destruction. (2) The uniaxial failure mode of the L-R-S-Ss is primarily split failure, with both vertical and oblique cracks, with the angle between the main crack and the vertical axis being less than 30°. (3) The content of the curing agent and the amount of water are important factors affecting the L-R-S-S strength. As the water content increases, the L-R-S-S compressive strength tends to decrease. The L-R-S-S strength increases with increasing amount of cementitious material. (4) A cubic polynomial and a rational fraction are used to fit the ascending and descending sections of the L-R-S-S stress–strain curves, respectively, and a piecewise constitutive model of the L-R-S-S specimens is proposed. The calculated results of the model are in good agreement with the experimental curves.