Study On Axial Compression Properties Of Tubular Triaxial Woven Fabric Composite Confined Concrete

Triaxial Woven Fabric（TWF）is composed of three groups of 60° yarns interwoven with each other.It has quasi-isotropy and has excellent mechanical properties as a composite material for reinforcement.It is widely used in sports and leisure,special protection,aerospace and other fields.In order to expand the application of triaxial woven fabric in the field of reinforcement,this paper adopts triaxial woven fabric to reinforce the concrete cylinder by winding.Digital Image Correlation（DIC）and Acoustic Emission（AE）were used to study the strain change and internal failure of the specimen during axial compression.Load-time curve,local strain-time curve and cumulative energy-time curve were obtained,the failure mode,ultimate load and axial strain of triaxial woven fabric confined concrete under different eccentricities are analyzed,through the yarn strain-time curve analysis of the three groups to fabric yarn under different stress conditions of stress,Compared with the cumulative energy-time curve,the energy absorption efficiency of the triaxial woven fabric was analyzed.In the loading process,the sample underwent three stress stages.In the first stage,the stress of concrete mainly led to the extrusion and friction of internal aggregate.In the second stage,the concrete is seriously damaged,and the outer triaxial woven fabric begins to play a restraint role,and the bearing capacity of the sample continues to increase until the peak value.In the third stage,cracks appear on the surface of the triaxial woven fabric,and the bearing capacity of the sample decreases.With the progress of compression,the cracks on the surface of the triaxial woven fabric are connected to form large cracks or the yarn is detached and bent,leading to complete failure of the sample.The performance of the triaxial woven fabrics with different components in the second and third stages is different,but with the increase of the eccentricity,the difference will gradually decrease.The test results show that the ultimate load of carbon fiber triaxial woven fabric confined concrete can be improved the most,while the ductility of glass fiber triaxial woven fabric confined concrete can be improved the most,and the ultimate load and ductility can be improved simultaneously by the carbon glass hybrid method.It should be noted that the hybrid mode has a certain influence on the mechanical properties.The mechanical properties of the sample with glass fiber as warp yarn and carbon fiber as weft yarn are improved more than those with glass fiber as weft yarn and carbon fiber as warp yarn.When the specimen is subjected to eccentric axial compression load,the ultimate load decreases and the failure mode changes with the increase of eccentricity,and the axial compression properties of different specimens are closer.The analysis of local strain-time curve of yarn obtained by DIC detection technology shows that the existence of eccentricity changes the stress environment of the sample.The stress state of the yarn under eccentric axial compression is more complex than that under forward axial compression.With the increase of eccentricity,the influence of axial force on the sample is gradually greater than that of annular force.Finally,through the force analysis of the samples,it is concluded that the triaxial woven fabrics of different materials directly affect the restraint effect of the triaxial woven fabric composites,and the increase of eccentricity reduces the main load-bearing yarn,which is the main reason for the decrease of the mechanical properties of the samples of different materials.