Preparation And Performance Test Of Composite Cable Cores

As of development economy,traditional overhead transmission cables have no longer met our demands for power increasing.It is impendent and important to develop a new kind of lines with large transmission capacity but low sag characteristic.Polymer matrix fiber reinforced composites are high temperature resistance,light weight,low thermal expansion coefficient and high specific strength. Using them as core instead of steel in Steel cored aluminum stranded cables can make cables function stably at higher temperature,which has been focused in the research field of new transmission materials.Here studied first on curing technology of composite cores based on three different matrix resins which are EP 618 system,GF-630 system and hydantoin EP system,explored the optimum adding amount of curing agent,and compared viscosity, pot life,curing agent's thermal stability of three EP systems.The conclusions show as follow.The optimum mechanical properties and curing degree was obtained as the adding proportions of curing agent were 75%,40%,35%each for three systems which were all close to stoichiometric proportions.Therefore,it could be acquired the optimum curing agent adding mount of each matrix systems.Among the three kinds of EP system,the viscosity of hydantoin EP system is less than 800mPa·s at 60℃,gelation time is more than eight hours,the tensile strength is 84.9Mpa.At the pressure of 31.0 MPa shear strength(metal to metal) is the highest, and its elongation is 3.3%,which matching with the matching with the aramid fiber's elongation at break.While the vitrification temperature T_g is 173.8℃,and by TGA we got three temperatures indexes T_s(193.3℃),T_A(193.3℃),T_zg(375.9℃), respectively,which is the highest.Accordingly,it is showed that in higher temperature, the hydantoin EP system is better with higher comprehensive properties.Then we got the samples of the composite cable core through the hand lay-up molding process,and the various performance indicators are analyzed.The density of the composite is 1.54g/cm³.at the same diameter and length,its quality reducts by 80.4%compared with that of steel core.DMA analysis was performed,the vitrification temperature is 157.8℃,the value of onset is 139.6℃;the linear expansion coefficient is lesser negative,in another word,there is no sag when the composite core under high temperature operation;the tensile strength,tensile modulus,the shear strength,the flexural strength and the bending modulus are 38.8KN(610.2MPa),79Gpa,37.8MPa,680.7MPa,19.9Gpa,respectively.The bonding situation between substrate resin and the enforced fiber interface was studied using Scanning Electron Microscopy(SEM).From the pictures,we found the bonding situation is good before the shear failure.After the shear failure,a certain amount of matrix resin was in fiber surface.The bonding situation is also good between subatrate resin and fiber interface.Analyzing the testing data,it can be concluded that main performances of composite cores prepared in the paper were far inferior to those of 1414 aramid fiber. These performances contain the tensile strength,the tensile modulus,the shear strength,the bend strength and the flexural modulus.Because composite cores were prepared with hand lay-up process in this paper,most of fibers had not totally stretched,and all of them could not bear power.If composite cores prepared were prepared with pulling and extruding molding process,their performances would improve by 5 times.In the end,the molding technology and equipments were designed,referencing to the extruding molding process of glass fiber composites,to prepare hydantoin resin matrix fiber reinforced composite cores.