Dynamic splitting behavior of hybrid fiber-reinforced geopolymers with high strength and toughness

Geopolymers, recognized for their low-carbon and environmentally friendly characteristics, are increasingly regarded as sustainable construction materials and potential alternatives to traditional cement-based materials. Hybrid fiber-reinforced geopolymer composites (HFRGPC), developed through fiber hybridization techniques, can effectively overcome the inherent brittleness and cracking tendency of geopolymers, thereby exhibiting high strength and toughness under static loading. However, systematic studies on their dynamic behavior remain limited. In this study, the splitting tensile behavior of HFRGPC was investigated using the Split Hopkinson Pressure Bar (SHPB) technique under six levels of impact air pressures (range 0.08–0.18 MPa). The failure modes, dynamic stress-strain responses, dynamic increase factor (DIF), and energy absorption characteristics were analyzed. Results show that fiber pull-out and fracture effectively suppressed crack propagation and delayed instability, with failure dominated by radial crack growth from the specimen center. The splitting tensile performance of HFRGPC exhibited pronounced strain-rate sensitivity, with the DIF increasing from 1.27 to 2.36 as the strain rate rose. A logarithmic model based on DIF values was established and demonstrated good predictive capability for the dynamic splitting behavior of HFRGPC. Moreover, energy transfer and transformation significantly increased with strain rate, with the fracture energy consumption of specimens rising by up to 200.87%. These findings provide experimental evidence for the potential application of HFRGPC in protective structures under impact loading.