Effect of fracture inclination on the fracture mechanics of simulated lunar regolith bricks

Understanding the influence of defects on crack initiation and failure modes in sintered lunar regolith materials is crucial for assessing the service performance of lunar base structures. In this work, microwave-sintered HUST-1 simulated lunar regolith bricks were prepared. The crack evolution and failure behaviour of single-crack samples with different prefabricated inclinations were analysed under uniaxial compression using a high-speed camera in combination with digital image correlation (DIC). Tensile, shear, and mixed cracks appeared at both ends of the prefabricated flaws. With increasing inclination angle, the overall mechanical performance of the bricks improved, peaking at 60°, where the maximum equivalent elastic modulus reached 17.657 GPa, corresponding to 93.12% of the control bricks. The failure pattern shifted from Mode I and mixed Mode I/II to predominantly Mode II. Additionally, many wing cracks extended into inclined secondary cracks, attributable to the stress field at the flaw tips changing from tensile-dominated to shear-dominated as inclination increased. Both alkali-activated and selective laser melting bricks contained initial defects. For engineering use, it is necessary to avoid aligning crack coalescence planes or tangential printing layers with the loading direction. Overall, microwave sintering is recommended as the more reliable processing method.