The Numerical Simulation Of Failure Process Of Hybrid Fiber Reinforced Concrete Based On Mesoscopic Scale

The hybrid fiber concrete is formed by mixing two or more kinds of fibers.With fully exert its "synergy" through reasonable matching,it can improving the mechanical properties of ordinary concrete,and the advantage is more obvious than that of single-fiber concrete.Therefore,it is also more susceptible to the promotion of engineering applications.At present,research on hybrid fiber concrete is still rare and concentrated at the macro level,and the research results obtained are difficult to explain the mechanism of meso-damage.The mesoscopic numerical analysis method can not only correctly reflect the heterogeneity and inhomogeneity of the material,but also avoid the adverse influence factors that may occur in the test,which is of great significance for the research of composite materials.In this paper,the mesoscopic numerical simulation method was adopted considering the shortcomings of macroscopic test of hybrid fiber concrete.Based on the random aggregate model,combined with the theoretical and experimental data,the appropriate material constitutive relationship is selected to establish the mesomodel of the hybrid fiber concrete.The uniaxial tension test of hybrid fiber concrete was simulated through the nonlinear finite element.According to the simulation results,the relationship between the meso-damage and macroscopic characteristics of the hybrid fiber concrete specimens and the mechanism of fiber cracking and toughening were analyzed.On this basis,the influence of meso structure,mechanical properties and structural form on the macroscopic performance of the test piece is considered.While saving the test cost and test time,further prediction analysis can be carried out on the basis of the original test.The main research ideas of this paper are as follows,1)Obtaining convex polygonal gravel aggregate of arbitrary shape by coordinate transformation of diamond parameter equation based on summarizing and improving the traditional algorithm.Furthermore,the algorithm for judging the intersection of fiber and polygonal aggregate is proposed.The two-dimensional meso-scopic model of hybrid fiber concrete is established by Matlab and Auto CAD.2)Based on the established hybrid fiber concrete specimen model,the numerical simulation of the uniaxial tensile test of the hybrid fiber concrete specimen was carried out.From the damage and macroscopic mechanical properties of the meso-scopic unit,the occurrence and expansion of the internal crack of the specimen were analyzed.The process,and its macroscopic mechanical response,is based on several effects of fiber on the crack propagation process.In addition,the influence of aggregate distribution on the macroscopic response of the specimen was also considered,and the stability of the model was verified.3)The uniaxial tensile test was carried out on the hybrid fiber concrete specimen model under the influence factors of different meso-scopic materials.The mortar strength,aggregate volume fraction,interfacial transition zone thickness and fiber content were studied for the hybrid fiber concrete test.The relationship between the equivalent elastic modulus,peak stress and peak strain is qualitatively analyzed.The relationship between mechanical property of hybrid fiber concrete in macro-scale and meso-structures is qualitatively analyzed.