Research On The Effect Of Steel Fibers On Crack Resistance Of Cement-based Composites

Steel fiber concrete is one of the most widely used building materials.The steel fiber used in steel fiber concrete has high tensile strength.The interaction between steel fiber and concrete makes up for the shortcomings of low tensile strength and poor toughness of concrete.At present,most of the research on steel fiber concrete is to study the steel fiber concrete as a macroscopic whole,and there is less research on the interaction between steel fiber and concrete.In this paper,by means of numerical simulation,the mechanism of steel fiber on the crack resistance of cement-based composites and the interaction between steel fiber and cement-based composites are studied,which provides a certain theoretical basis for the application of steel fiber concrete.The research content and results are as follows:(1)Based on the cohesive model,the entire pull-out process of a single steel fiber in the cement-based materials was numerically simulated.The influence of steel fiber bond length and the pull-out direction on the ultimate pull-out load was analyzed and the pull-out curve was obtained.(2)The constitutive model of the steel fiber in the numerical simulation was converted with the pull-out curve and a steel fiber pull-out failure model(FPFM)was obtained.With the FPFM model,during the simulating of the bond-slip between steel fiber and cement,the great amount interface contacting calculation could be avoived,which provides an effective way for the numerical simulation of steel fiber reinforced cement-based materials in complex structure.(3)Randomly distributed steel fibers in a two-dimensional three-point bending beam were generated through Python,combined with FPFM and extended finite element simulation,the whole process of crack generation and propagation was studied.Through fracture parameters such as crack tortuosity and fracture energy,as well as tensile damage of the cement-based materials,the toughening and crack resistance ability of steel fiber on cement-based materials and the influence of steel fiber on the crack shape of cement-based materials were analyzed.(4)Randomly distributed steel fibers in a three-dimensional three-point bending beam were generated through Python,and the simulation was carried out by combining FPFM and extended finite element simulation.The crack resistance ability of steel fiber volume ratio and steel fiber position on cement-based materials was analyzed,and the stress in steel fiber in the whole simulation process was studied.The results show that 1.5% volume fraction of steel fiber cement-based composite has the best comprehensive properties,and the steel fiber in the middle tensile zone of beam has the best toughening and crack resistance.(5)A steel fiber reinforced cement-based beam with I-notch was designed for three-point bending experiment.The experimental results were compared with the simulation results,which verifies the correctness of the FPFM model and the numerical calculation.