Characterization And Analysis Of Tensile And Fracture Mechanical Behavior Of Cotton Fibers

Cotton is not only the main material of the textile industry,but also an important strategic material of the country,occupying an important position in the national economy.From picking to product application,cotton has to go through multiple processing procedures such as harvesting,tying,spinning,weaving and finishing.In each process,cotton fibers will be damaged and broken by various mechanical external forces,among which mechanical stretching is the most basic form of force that causes cotton fibers to be damaged and broken,which seriously affects the subsequent processing efficiency and products of cotton fibers.Use performance.Therefore,this paper focuses on the research on cotton fiber tensile fracture damage,and analyzes the tensile mechanical properties and fracture mechanism of cotton fiber,which has important guiding significance for cotton harvesting,cotton spinning enterprises’ production and processing,and fiber quality inspection.This paper takes Xinjiang long-staple cotton fiber as the research object,adopts the method of physical experiment,and carries out the cotton fiber tensile experiment with the help of the fiber tensile mechanical shape tester,and analyzes the relationship between the cotton fiber tensile mechanical properties and the fiber shape change.The fracture damage experiment of a single cotton fiber was carried out with the help of acoustic emission testing device and scanning electron microscope,and its fracture mechanism was further revealed by using various characterization methods.The results show:(1)Fiber diameter,specimen length,tensile speed and different fiber structures have influences on the mechanical properties of single cotton fibers.When the length of the specimen and the tensile speed are constant,the breaking strength of a single cotton fiber gradually decreases with the increase of the diameter of a single cotton fiber,and when the fiber diameter is fixed,the breaking strength of a single cotton fiber increases with the increase of the tensile speed and decreases with the increase of the length of the specimen,while the elongation at break of a single cotton fiber is not affected by the tensile speed,but will increase with the increase of the length of the fiber specimen.(2)The mechanical properties of a single cotton fiber are not only affected by the single influence of three factors,but also by the interaction of three factors,and the order of influence is fiber diameter> tensile speed > specimen length.When the fiber specimen length is 3mm,the fiber diameter is 22.64 μm,the tensile speed is 6 μm/s,and the breaking strength of cotton fiber is 50.7 m N,the mechanical properties of a single cotton fiber are the best.The breaking strength of cotton fibers was characterized by the traditional Weibull distribution model,and the modulus decreased with the increase of fiber length.There is a good correlation between the predicted value of cotton fiber breaking strength and the true value,and it is concluded that the traditional Weibull distribution model can be used to characterize the discreteness of cotton fiber breaking strength.(3)Through the comparison and analysis of different fiber structures and the mechanical properties of single and multiple cotton fibers,it is found that a single cotton fiber shows two types of mechanical characteristic curves: direct fracture and gradual fracture during the stretching process.These two curves correspond to There is a direct relationship between the morphological changes.The mechanical properties of different fiber structures are quite different.During the stretching process of multiple cotton fibers,the mechanical property index value does not follow the multiple growth law of the mechanical property value of a single cotton fiber,and the fracture form is one by one.(4)The energy produced by a single cotton fiber during the fracture process decreases with the increase of the sample length,and small energy fluctuations lead to a decrease in the activity of the acoustic emission event,and at the same time appear as a weaker acoustic emission signal.The process of cotton fiber fracture and damage is mainly divided into three stages,which are the stage of straightening state during clamping,the stage of basic fibril crack generation,the stage of basic fibril delamination and microcrack propagation,and the stage of basic fibril fracture.The fiber fracture modes can be summarized into four types:direct fracture,axial fracture,torsional fracture,and slip fracture between fiber filaments.