Research On Fracture Characteristics And Theoretical Model Of Aligned Steel Fiber Reinforced Cement-based Composites

Aligned steel fiber reinforced cement-based composite(ASFRC)is a new type of composite material formed by manually controlling the distribution direction of steel fibers in a cement matrix.A number of studies have shown that the mechanical properties of ASFRC are better than those of ordinary steel fiber-reinforced cement-based composites when the direction of the principal tensile stress is the same as or close to the fiber direction.In this paper,the three-point bending test on notched beams of ASFRC was conducted.The fracture properties of ASFRC were studied using experimental research and theoretical analysis.At the same time,the theoretical analysis of the whole fracture process of ASFRC was carried out.The specific research content is shown as follows:(1)The fracture process of ASFRC was studied by using the three-point bending notched beam test.The influence of steel fiber content,steel fiber distribution and water-cement ratio on the fracture performance of ASFRC was studied.The fracture process curve and fracture parameters of ordinary steel fiber reinforced cementitious composites and ASFRC were compared.The results show that the fracture performance of steel fiber reinforced cement-based composites can be improved by aligning steel fibers,increasing content of steel fibers and decreasing the water-cement ratio.(2)The damage and fracture process of ASFRC was studied by using the Digital Image Correlation Method(DIC).The strain and displacement distribution at different load moments were obtained.The results obtained by DIC and those obtained by traditional displacement meter were compared.The strengthen and toughening mechanism of ASFRC was analyzed.(3)A nonlinear hinge model based on toughness criterion was established.The whole fracture process of ASFRC was analyzed theoretically.The theoretical method was verified by experimental results and the parameter sensitivity of the model was studied.The results show that this model can predict the fracture process of ASFRC with different steel fiber content.