Analysis On The Structure And The Tensile Property Of The Flame Retardant Three Component Composite Yarns

The research on the structure and mechanical properties of yarn is a classic problem.The structure of the yarn can be divided into several forms according to different rules,such as the compact and open stacking form,the strong twist and weak twist form,and the blended and composite forms.As the mechanical behaviors of these yarns are different,on the condition of the definite structure expression,it is need to demonstrate diverse mechanical behaviors through the mechanical model.In this paper,PBO(poly-p-phenylene diphenyloxazole)filament,aramid filament,flame retardant polyester filament and flame-retardant polyvinyl alcohol filament are set as the research object,the tensile properties of composite yarns is modeled and analyzed by the classical mechanical model and statistical model,besides,the computer simulation is employed to analyze the tensile strength of the three-component composite yarns.Analysis on yarn fitness and other parameters can provide reliable data and scientific advice to the design of composite yarn,the screening of fiber content and the determination of yarn forming process,furthermore,it can also provide a theoretical method for estimation on the tensile properties of composite yarn.In this paper,the linear density and diameter of monofilament is measured at first,the density of fiber can be calculated subsequently,then the accuracy of calculated results is verified,finally the diameters of PBO(poly-p-phenylene diphenyloxazole)filament,aramid filament,flame retardant polyester filament,flame retardant PVA filament and flame retardant viscose fiber are measured by interrupted cutting weighing,microscope and image analysis method.In addition,the tensile properties of the fibers are tested,the difference of tensile curve and parameters(fracture strength,fracture elongation,initial modulus and fracture work ratio)among these filaments is compared as well.Due to the classical analysis of tensile curve,aramid filament and flame retardant viscose filament demonstrate quasi linear behavior at the posterior of curve,while PBO presents top convex shape,flame retardant PVA filament below concave and flame retardant polyester filament non-linear double-step.Results shows that fracture strength is linearly correlation with fracture work ratio.Fracture strength distribution of fiber,on the basis of Gauss distribution model and Weibull distribution model,is fitted and analyzed.The analysis results illustrate that Gauss distribution is the most accurate solution to estimate strength distribution of flexible fiber.Friction coefficient among filaments is measured,and results illustrate that friction coefficient between the same kind of fiber is not less than that of different fibers,for it is relevant to self-material.That is,the total friction coefficient of two fibers with different friction coefficient is larger than the average friction coefficient.The fracture strength of multi-fibers is analyzed through statistical analysis method in this paper.On the basis of definite tensile property,the structure and tensile property of three-component composite yarn is measured.The radial distribution of fibers in the composite yarn can be demonstrated through staining slice method and Hamilton Transfer Index,then combined with mechanical characteristic of threecomponent composite yarn model and structure parameters of yarn,two kinds of ideal yarn structure models can be obtained,that is,optimal mechanical model and optimal flame retardant model.In this paper,the tensile curve of three-component composite yarn can be synthesized by Matlab,and the difference between obtained curve and measured tensile property is analyzed subsequently,then the tensile behavior characteristic of composite yarn is illustrated and the fracture strength distribution of yarn is fitted and solved.Analysis results shows that Gauss distribution is the most optimal solution.Combined with appropriate yarn structure,on the basis of mechanical characteristics of corresponding filaments,classical Vangheluwe tensile model and modified Vangheluwe model with matrix method,which is introduced for solving nonlinear equation constants,are employed to fit the tensile behavior of three-component composite yarns.The results demonstrate that the modified Vangheluwe model can improve the defect that the modulus is not zero when the strain is equal to zero.