Research On Strength And Deformation Characteristics Of Vectran Fiber Closed Braided Rop

High performance fiber braided rope represented by polyarylate fiber has the characteristics of light weight,wear resistance,high low temperature resistance,strong designability and so on,and has gradually become an important part in the field of spacecraft lightweight technology.In order to make braided rope used in special working conditions,such as mesh deployable antenna and thermal knives holddown and release system,it is necessary to connect the braided rope end to form a closed rope loop.When it is used as a closed rope loop,the mechanical properties of the closed connection area of braided rope often become the weak links of the strength of the braided structure.Therefore,the aim of this study was to focus on the strength and deformation characteristics of Vectran fiber linked braided rope for the application requirements of braided rope loop used in spaceflight.Firstly,two kinds of linear density of high-load braided ropes were designed and braided using polyarylate fiber.Then,the effects of braided pitch,preloading level drawing speed and on the tensile properties of polyarylate fiber braided ropes were studied.The results showed that with the increasing braided pitch of the rope,the tensile strength was increased and the elongation was decreased.Preloading could effectively improve the tensile strength of braided ropes.Contrast with no preloading,the tensile strength of the two ropes were increased by 11.7% and 12.1%,respectively,at the maximum strength.For braided ropes of the same linear density,the drawing speed had little influence on the strength of the braided ropeThen,the closing methods of two kinds of linear density braided ropes were introduced mainly from the aspects of knotting,splicing and stitching.This included five types of knots,three splicing processes and five stitching parameters.The effect of various factors upon the strength of the link braided ropes were investigated and the deformation relevance of the results were discussed.(1)Among the five knots,the load capacity of the knot is lower,and the joint efficiency of the hunter’s knot with the highest strength is 14.8% and 15.8% higher than that of the reef knot with the lowest strength.(2)In the splicing process,the overall joint efficiency is high,the minimum is 87.7%,the maximum is 100.8%.(3)In different stitching parameters,when the of thread is Kevlar 1000D/3,the stitch type is 301 and the stitch pattern is crossed,the joint efficiency of braided rope is the highest.The load of lined braided rope increased firstly and then decreased with the increase of stitching length and spacing,and reached the maximum value when the stitching length was 20 times of diameter and stitching spacing was 5mm,respectively.The tensile failure of the linked braided rope starts from the fracture of the braided yarn at the end of the joint.In the connecting,the braided structure is deformed,the braided yarn is pulled out,and the phenomenon of broken and drawn wire is serious.Finally,for the closed braided rope loop with stitching,stress relaxation tests were performed for 168 hours at 50% and 75% stress levels respectively.The results showed that 12 hour at the beginning of the experiment,the stress value decreases rapidly,until the end of the experiment,the stress of the closed braided rope loop decreased by 14.2% and 15.1%,respectively,at the two stress levels.