Steel/plastic-steel hybrid fiber UHPC dynamic tensile performance: An experimental and numerical simulation study

Abstract

Steel fibers (ST) in Ultra-high performance concrete (UHPC) play an important role in enhancing its mechanical strength and toughness. However, the brittleness of UHPC increases significantly under dynamic loading, while the contribution of ST to its tensile strength and fracture mode is relatively limited. In this study, Ultra-high performance hybrid fiber reinforced concrete (UHP-HFRC) was prepared using four hybrid ratios of ST and plastic steel fibers (high-performance polypropylene, PSF), and a series of quasi-static and dynamic splitting tests were conducted to investigate the effect of PSF on its dynamic tensile behavior. Additionally, X-ray computed tomography (X-CT) and SEM characterization techniques were applied to reveal the fiber synergy effect and enhancement mechanisms from the perspective of microcrack development. In addition, a novel hybrid fiber modeling method is proposed for finite element simulation of the dynamic tensile response of UHP-HFRC. The results indicate that fiber hybridization reduces the degree of damage of UHPC under dynamic loading, and its contribution is influenced by the strain rate. The increase in steel fiber content increases the dynamic tensile strength of UHP-HFRC, but the increase in PSF content contributes to the increase in energy absorption at fracture, and it is recommended to use 1 % of PSF mixed with ST. The simulation results show the constitutive relationships and failure modes that agree with the impact test results, verifying that the proposed three-dimensional mesoscopic model can effectively analyze the dynamic splitting performance of UHP-HFRC.