Study On Uniaxial Tensile Properties Of Textile Reinforced Cement-based Composites

Compared to common reinforced concrete and short fiber reinforced cement-based composites,cement reinforced by textile which is woven by fiber bundles in two-direction can deal with the problem of reinforcement corrosion and improve the effectiveness of fiber.In the engineering practice,some structure members are subjected to tensile stress for a long time.The composites under uniaxial tensile stress exhibits non-linear properties due to the influence of the interfacial bonding between textile and matrix,and the mechanical properties of composites are very complex.Experimental and theoretical studies of the mechanical properties of textile and matrix,bonding properties between textile and matrix and uniaxial tensile properties of textile reinforced cement-based composites were conducted to understand the bonding mechanism and tensile behavior of the composites.Uniaxial tensile curve model was established,which provides the theoretical basis of promoting the application of the composites.The following works were mainly carried out in this paper:1.The bonding properties between textile and cement matrix(1)Experimental study: 18 groups of specimens were prepared and pull-out tests were conducted,the different factors influencing on the interfacial properties of the composite materials were studied.The test results showed that the failure state was mainly decided by the embedded length of textile.With the increase of embedded length of textile,the ultimate pullout load of specimens improves,interfacial bonding strength decreases and the linear slope of test curve also decreases.Compared to fiber bundles specimens,the bond strength textile reinforced specimens is higher.When textile impregnated by epoxy resin,it could gain more global stress,and fine sand adhesion was conducive to the bond anchorage properties of textile in the matrix.Increasing specimen thickness could significantly improve the ultimate pullout load of specimens.(2)Theoretical analysis: Based on the experimental results,the pull-out behavior was analyzed.The model for calculating the nominal shear strength of specimens with different thicknesses was established.The calculated results were in a satisfactory agreement with the experimental values.2.Uniaxial tensile properties of composites(1)Experimental study: Uniaxial tensile specimens consisting 1-3 layers textile were prepared by using self-designed mold.Uniaxial tensile tests on 10 groups of specimens were conducted to get the uniaxial tensile curves,and the different factors influencing on tensile properties were also studied.The results showed that the uniaxial tensile process of specimens with surface treatment could be divided into four stages,while the multi-cracking state of uniaxial tensile process of specimens without surface treatment is not obvious,most of which failed because of slipping.The cracking load of specimens increased and the utilization ratio of fiber decreased when textile layers increase.The textile with surface treatment could effectively improve the performance of the bonding between fibers,and the ultimate loads the utilization rate of fiber were also higher.Adding PVA fiber in the matrix could change the damage state,and improve the ultimate bearing capacity of the specimen and tensile toughness.(2)The theory of complete curve constitutive model: Based on different curves of composite and stiffness variation in the whole process of uniaxial tensile tests,the more simple constitutive model with clear physical meaning was established.The results agree well with the experimental results,and reach the requirement of engineering application accuracy.