Experimental Study On Dynamic Properties Of Fiber Reinforced Concrete Under Impact Loading

Fiber reinforced concrete (FRC) is made of hydraulic cements containing variously sized aggregate, randomly oriented fibers and slurry. In the FRC, the fiber can prevent the crack of the concrete matrix from extending effectively under loading; it can optimize and improve the mechanical behavior of materials. Because of these advantages, the FRC has been the main building material of many large-scale constructions and military bunkers now. Many scholars have not yet started on the dynamic properties of fiber concrete research; this is precisely the work of the research on the dynamic characteristics. This study can provide FRC structural design, preparation and optimization of reference, and has important scientific significance and practical value.Firstly, the thesis reviews the present situation about the dynamic mechanical behavior of concrete research at home and abroad. There are significant differences between the impact of dynamic mechanical properties of concrete and the static case. And so far experimental data published on the concrete is still controversial at high strain rate. At present, for the description of dynamic behavior of concrete has not reached a consensus. Split Hopkinson pressure bar (SHPB) technique has been used widely to measure the dynamic strength enhancement of concrete-like material at high strain-rate between 10-1 and 103s-1. This thesis summarizes problems and related solutions about the SHPB experimental technique of concrete.This thesis focuses on the static and dynamic mechanical properties of the polypropylene fiber and steel fiber reinforced concrete. Splitting tensile fracture of fiber reinforced concrete is experimentally studied related to failure. Among them, the steel fiber reinforced concrete (fiber volume fraction of 1%), polypropylene fiber reinforced concrete (fiber volume fraction of 0.1%, 0.2%,0.3%) and mixed fiber reinforced concrete (steel fiber and polypropylene fiber volume fraction of 1%,0.1%) had the static and the impact of uniaxial compression tests and splitting tensile tests under variety of strain rates. In order to ensure the accuracy of SHPB experiment, considering the incident wave, strain rate range, interfacial friction and inertia effects, and other major factors.Through processing data, it has been known that there is the strain rate response of fiber reinforced concrete in tension, compression, toughness. Studies have shown that significant enhancement of fiber, fiber content the greater the strain rate effect is more obvious, the more excellent impact resistance. There are curve relationship between dynamic relative compressive enhancement factor and strain rate's index, and strain rate threshold is about 40s-1. By the Gaussian fitting method, we obtain the corresponding relation. There are linear relationship between dynamic relative tensile enhancement factor and strain rate's index, and strain rate threshold is about 3.6s-1.