Experimental Study And Finite Element Simulation Of Low-Speed Impact For Ultra High Performance Fiber Reinforced Concrete (UHPFRC)

Ultra High Performance Fiber Reinforced Concrete (UHPFRC) composed of the matrix named Ultra High Performance Concrete (UHPC) and the random-oriented steel fiber, is a kind of multiphase inhomogeneous composite material. The matrix possesses ultra-high strength that the ordinary concrete cannot surpass. Furthermore, the toughening and crack resistance effects of the steel fibers improve the mechanical performance of UHPFRC, resulting in good application prospects of UHPFRC in the construction engineering and the military protection engineering. In this thesis the mechanical behavior of UHPFRC materials is studied by an approach combining experiments and finite element simulation method and the main contents include:1. The UHPFRC specimens were prepared using the traditional mixing method, the steel fiber volume contents of which are 0%,1%,2%, and 3% respectively. The cube compression tests, the trabecular four-point bending tests and the low-speed impact tests were performed. The compressive strength, flexural strength, load-deflection curve, strain changes of key positions, strain field of the pure bending section, destruction of the impact surface, etc. were obtained. The static and dynamic mechanical behavior of UHPFRC material with the incorporation of steel fibers and the changing of the volume content were studied. The failure process or failure modes under various experiments were analyzed. The role of fiber and failure mechanism was described briefly.2. The HJC model was introduced briefly and the parameter types were classified. The parameter sensitivity analysis on the parameters of relevant literature was performed, the impacts on the crater depth and diameter of each parameter were obtained; the detailed process of the parameters was given and some reasonable suggestions were presented.3. Finite element simulation for low-speed impact experiment of UHPFRC materials were performed using the ANSYS/LS-DYNA numerical software and the parameters taken according to the HJC model. With the detailed process of finite element model, the destruction situations and the destruction process of UHPFRC target body were analyzed integrally. The simulation results under different impact velocity and different fiber contents were displayed systematically. The simulation results and the experimental results were compared to verify the rationality of HJC model parameters.