Dynamic Damage Constitutive Relationship Of Hybrid Fiber Reinforced High Strength Concrete

Two or more of the hybrid fibers are added to the concrete matrix, in which interweave the perplexing network, and have a "stable" effect on concrete materials, reinforce and toughening the concrete matrix, and synergy to enhance strength and toughness of the matrix.The technology and mechanical properties of the hybrid fiber reinforced high strength concrete(HFRHSC) are carried out in this paper.The preparation of the steel fiber volume fraction is 0 to 4 percent, polypropylene fiber volume rate is 0 to 0.1 percent, parameters of fly ash is 0 to 30 percent, silicon powder content is 0 to 20 percent, and strength grade of the HFRHSC is C40 to C80. Studying the lever of these four factors on HFRHSC mechanical property and shock resistance research, theoretical analysis and numerical simulation, the main research results are as follows:The infiltration of the hybrid fiber has a certain effect on enhancement and toughness to the concrete matrix, and play s a role in "resistance" to the cracking. The steel fiber is the most evident. The incorporation of fly ash content within 15 percent can effectively enhance the concrete workability and show good construction performance. The compressive strength of the concrete matrix have obvious enhancement effect. But more than the limit value, it will have a reduced effect. The main reason is that with large amount of fly ash, the consumption of cement will be small, and the generation of high strength cementitious products will be relatively small, thereby reducing the strength of concrete matrix.SHPB dynamic compression test shows that the mixed fibers improve the biting force of internal cementing materials of the specimens, and significantly enhance the dynamic compressive strength of the concrete matrix. In addition, concrete is a kind of strain rate sensitive material. When the strain rate is more than the sensitivity threshold(51/s~56/s), the destruction of concrete specimen will occur. And strain rate doesn’t meet the threshold, the concrete peak stress will be less than the static compressive strength. In this stage, with thechange of strain rate, the change of peak stress is small, and the specimens after dynamic test will have no significant damage.Based on the fractal theory, the fractal dimension is used to quantitative analysis of the internal evolution of micromechacal damage behavior of concrete material, and the quantitative analysis on the dynamic damage factor is adopted. From the microscopic study of the relationship between organizational structure and material performance of concrete materials, the dynamic damage constitutive relationship of SHPB considering fractal damage evolution is established, and the experimental data of HFRHSC blocks under the condition of dynamic compression test is verified.By using the software ANSYS/LS-DYNA for simulation of the HFRHSC dynamic compression test, the failure process of blocks under a transient shock is reproduced, the damage forms of HFRHSC blocks at different time are obtained, and the damage forms of specimens under different strain rates are studied and analyzed from the stress wave. The numerical simulation results fit well with the experimental results. There is reference significance on the HFRHSC dynamic damage evolution.