Finite Element Simulation Of Strain Hardening Fiber Reinforced Cementitious Composites

Strain-hardening fiber reinforced cementitious composite is a kind of reinforced cementitious composites material with high toughness,and ECC(Engineered cementitious composites),as one of the typical representative of high toughness materials,the ultimate tensile strain of the material can reach more than 3% based on micromechanics and fracture mechanics theory.ECC starts late in China but has a very fast development.Most of the researchers focused on the experimental research of ECC.Finite element simulation and practical application of ECC are lacked,besides,a lot of manpower and material resources are needed in experiments.In this paper,a new modeling method of ECC material is put forward from the point of view of numerical simulation,and the mechanical properties of the material are studied by using the finite element model put forward.In view of this,this paper uses the finite element software ABAQUS,and establishes a three-dimensional two-phase mesoscopic finite element model,considering the interface interaction between the fiber and matrix.This model can realize the simulation of the ECC material effectively,and afterword study the corresponding parameters on ECC's mechanical properties.The main works are listed as follows:(1)A random delivery process of fiber by using the Monte Carlo method is established.Then this article studies the corresponding algorithm using MATLAB programming language,and accomplishes the fiber's cross section random delivery in two-dimensional space,the fiber's longitudinal section random delivery in two dimensional space,the entity fiber's 3D random distribution in three dimensional space,as well as the linear fiber's random distribution in three-dimensional space,paving the way for the establishment of finite element model.(2)By using ABAQUS finite element simulation software,using truss element as fiber and C3D8 R element as matrix,and using plasticity damaged model as matrix's constitutive model and fiber-interface joint constitutive model based on single fiber pull-out test as fiber's constitutive model,the fiber is embedded in matrix and three-dimensional two-phase finite element model is established.(3)Using the finite element model proposed to simulate the uniaxial compression test and the four-point bending test of ECC,the validity of the model was confirmed by comparing the model's result with the experimental results in the literature.And the parametric analysis was carried out using the FEA model by changing the volume fraction of fiber,matrix cracking strength,and initial sliding friction stress.For compression,the compressive strength and the peak strain did not change significantly with the increase of fiber volume fraction,but the toughness after the compression failure of ECC improved obviously.For bending,the 2% fiber by volume content is the critical volume fraction of the ideal strain hardening phenomenon.With fiber volume fraction increasing,the bending toughness of ECC will increase significantly.To reduce the matrix cracking strength contributes to increase ECC strain hardening capacity.However,it will reduce the bending peak load of specimen.The bending peak load is positively proportional to initial sliding friction stress0? while the effect of flexural toughness is not a simple linear relationship with0?.For specific fibers and matrix,there exists an optimum0? making the bending toughness of ECC to reach maximum value.