Investigation of mechanical properties and reaction mechanisms of potassium hexatitanate whisker-reinforced geopolymers based on lunar regolith simulant

To enhance the mechanical performance and microstructural characteristics of the lunar soil simulant geopolymer, the reinforcing effects and underlying reaction mechanisms of potassium hexatitanate whiskers (PHW) were systematically investigated. PHW were incorporated into the lunar soil simulant geopolymer at varying mass fractions (0 %, 0.2 %, 0.4 %, 0.6 %, and 0.8 %). The resulting mechanical performance and microstructural evolution were comprehensively characterized through uniaxial compression and tensile testing, thermogravimetric-differential thermogravimetric analysis (TG-DTG), scanning electron microscopy (SEM), X-ray diffraction (XRD), digital image correlation (DIC), and Fourier-transform infrared spectroscopy (FTIR). Through quantitative analysis of the mechanical damage process and microstructural evolution, the effect of PHW on reinforcing the mechanical performance and elucidating the reaction mechanism of the geopolymer was thoroughly investigated. Compared to the 28 days reference sample without PHW, the simulated lunar soil geopolymers incorporating 0.2 % and 0.4 % PHW exhibited optimal compressive strengths of 35.808 MPa and 34.664 MPa, representing enhancements of approximately 24 % and 20 %, respectively. The specimens containing 0.2 % and 0.4 % PHW achieved tensile strengths of 5.854 MPa and 6.0735 MPa, respectively, reflecting improvements of approximately 12 % and 16 % over the reference sample without PHW. DIC analysis reveals that with increasing PHW content, the strain field distribution becomes more uniform, and the rate of crack propagation diminishes. The incorporation of PHW significantly enhances the crack resistance of the specimens, exhibiting a pronounced crack-bridging and control effect. SEM, XRD, and FTIR analyses confirmed that the whiskers were homogeneously dispersed within the geopolymer matrix, establishing effective bridging and anchoring structures. These whiskers interacted synergistically with the (N,C)-A-S-H gel, forming a robust three-dimensional network that reinforced the matrix’s structural integrity, refined the pore architecture, reduced overall porosity, and consequently enhanced both the mechanical performance and the stability of the material. TGA analysis indicates that the incorporation of whiskers enhances the thermal stability of the geopolymer matrix and effectively reduces high-temperature mass loss. The bridging and anchoring mechanisms imparted by the whiskers contribute to the structural resilience of the material, offering theoretical insights and a solid technical foundation for the prospective application of geopolymer composites in lunar base construction. • Potassium hexatitanate whiskers (PHW) represent a class of ultra-short fibrous reinforcements acclaimed for their superior mechanical performance and remarkable thermal stability. • The incorporation of potassium hexatitanate whiskers (PHW) into geopolymer structural composites synthesized from lunar regolith simulants markedly elevates their overall mechanical performance. • SEM observations reveal that potassium hexatitanate whiskers (PHW) facilitates gel condensation and refines the pore architecture as well as the density of the interfacial transition zone. An appropriate dosage effectively reduces porosity, whereas excessive incorporation induces agglomeration and interfacial defects.