Influence of fiber type on the mechanical performance and fracture mechanism of fiber reinforced concrete under coupled static-dynamic compression

Abstract

As a high-performance building material, fiber-reinforced concrete (FRC) has attracted garnered significant interest in practical engineering construction. However, the effect of coupled static-dynamic loading on the dynamic response of FRC remains far from understood, which seriously limits its wide application. In this study, a series of coupled static-dynamic loading tests are conducted on four types of FRC specimens using the modified split Hopkinson pressure bar (SHPB) system, and the influences of static pre-stress and strain rate on the mechanical performance of FRC under coupled static-dynamic loading are systematically analyzed. The experimental results indicate that static pre-stress generally reduces the dynamic strength and energy dissipation density, but increases the total strength and fragmentation degree of FRC. As the pre-stress ratio increases from 0 to 0.6, the dynamic strength of FRC decreases ranging from 12 to 25 %, and the total strength increases ranging from 12 to 34 %. The failure features of FRC specimens changes from tensile failure mechanism to tensile-shear mixed mechanism with increasing the static pre-stress. Combining the scanning electron microscope (SEM) and mercury intrusion porosimetry (MIP) techniques, the microscopic structure and fracture mechanisms of FRC specimens are revealed, and the underlying influencing mechanisms of the static pre-stress, strain rate and fibers are further discussed. The axial pre-stress exerts a dual effect on FRC: enhancement by compacting primary voids as well as attenuation by stimulating secondary microcracks. The strain rate dominates the mechanical performance of FRC under coupled static-dynamic loading, and the influence of pre-stress is diminished by higher strain rates. In addition, the fiber incorporation strengthens the concrete pore structure by bridging action and crack inhibition, resulting in superior mechanical performance compared to normal concrete under coupled static-dynamic loading conditions.