Dynamic Fracture of Fibre-Reinforced Concrete Depending on the Shape and Material of the Reinforcing Fibre

The strain rate sensitivity of the compressive strength of fibre-reinforced concrete (FRC) to the applied load, which is observed during dynamic loading, is analysed based on the incubation time criterion. For each FRC specimen with a different fibre volume fraction, the incubation time is determined as a scale-dependent, basic measure of the material's response to high-speed loading and as a characteristic that is invariant with respect to the loading rate. Using FRC with steel, ceramic, and carbon fibres as an example, the effect of adding straight fibres on the dynamic strength and incubation time of FRC is considered. The existence of fibre would increase the concrete quasi-static strength but weaken the strain rate effect of FRC with straight steel fibres characterized by the ratio of dynamic strength with quasi-static strength, which even result in lower dynamic strength of FRC with straight steel fibres. A comparison of the strain rate dependence of the strength of FRC with spiral and straight steel fibres is provided. The dependence of incubation time on the volume fraction of fiber for FRC with straight steel fibres is proposed.