Study On Compressive And Flexural Properties Of Artificially Directional Steel Fiber Reinforced Cementitious Matrix Material

Fiber reinforced cementitious matrix(FRCM)is a new type of composite material in which chopped fibers are added into cement matrix composite materials in order to improve the overall performance.As a high tensile material,chopped fiber is the main part to share the stress of FRCM.The traditional preparation method of FRCM is to mix the fiber and cementitious material directly and pour them into the mold.The chopped fiber presents a randomly distributed fiber orientation in the substrate,and there is an angle between the fiber direction and the stress direction,resulting in the limited contribution of the fiber to the improvement of the mechanical properties of FRCM.Therefore,in this subject,the directional steel FRCM is prepared by means of artificial orientation,selecting shear steel fiber and milling wavy steel fiber which are convenient for orientation.In this paper,the effects of fiber orientation,fiber type,fiber content and fiber layout on the mechanical properties of directional FRCM are explored through compressive test and flexural test.The main research results are as follows:(1)The artificial orientation method which prepared Steel FRCM materialsTo prepare steel FRCM by artificial orientation method,it is necessary to control the ratio of water to cementitious material of the substrate,so that the cement matrix composite has low fluidity and can maintain the original position after the fiber is placed.At the same time,the cement matrix composite needs to have good plasticity to ensure that it can flow smoothly by external disturbance during pouring.To solve the proportioning problem of cement matrix composite materials,focus on the preparation process and method of cement matrix composite materials.(2)Effect of directional fiber on compressive properties of FRCMIn the compressive test,the effects of fiber orientation,fiber type and fiber content on the compressive properties of FRCM are analyzed.When 90°oriented,the fiber direction is consistent with the direction of cement matrix composite compression diffusion,which can provide the highest compressive strength.The compressive strength of oriented fiber specimens with different orientations shows the order of 90°> 45°> 0°.Milling fiber has the best effect on improving the compressive strength,and the effect of shearing fiber is general.Through strain measurement,it is analyzed that the fiber inhibits transverse deformation,it is proved that when the fiber orientation is parallel to the surface of the test block,the fiber has a significant inhibitory effect on the increase of surface strain.If there is an angle between them,the inhibitory effect will be reduced,and the surface may crack,making the strain increase faster.The higher the fiber content and the better the fiber orientation is,the smaller the vertical deformation is,and the fiber content has the greatest influence.(3)Effect of directional fiber on flexural properties of FRCMIn the flexural test,the effects of fiber orientation,fiber type and fiber layout on the flexural properties of FRCM are analyzed.Similarly,90° orientation and milling fibers provide higher flexural strength.The mid span deflection of the beam can reach a larger displacement value,which makes the area enclosed by the load-mid span deflection curve of the beam and the X-axis larger,with higher energy consumption and higher flexural toughness factor.The order of flexural strength of specimens with different fiber orientation and arrangement is 90° full arrangement > 90° half arrangement > randomly distributed fiber orientation.The half arrangement is that the fibers are only arranged in the main tensile stress area of the beam,its performance and various parameter indexes are slightly less than those of90°full arrangement specimens,which has high cost performance.In the strain analysis,the experimental results show that the fiber has better inhibition effect on cement matrix composite cracking when the fiber is fully arranged at 90°,and the substrate and fiber in the main tensile stress area show better synergistic deformation.