Research On Fabrication And Energy-absorbing Characteristics Of Carbon Fiber Strengthened Thin-walled Steel Tubes

With the increasingly serious problems of energy sources,environmental protection and road safety,more and more attention has been paid to the issue of Lightweight of Automobile and Safety of Automobile.Therefore,in this paper,CFRP material and steel are combined.We coated CFRP material outside the steel tubes to make carbon fiber strengthened thin-walled steel tubes(referred to as composite tubes).It combines the characteristics of light weight and high strength of CFRP with the good deformation of steel,and induces the deformation of the outer CFRP material through the progressive collapse deformation of the internal steel tube.This kind of composite tubes belongs to the innovative application of automobile safety components and can be used to guide the design of crash box,and at the same time conforms to the issue of Lightweight of Automobile.The main work and results are as follows:(1)The material properties of the composite tubes were studied and the following conclusions were drawn:The working temperature、curing system、the glass transition temperature and mechanical properties of CFSR-A/B epoxy resin system in CFRP material were determined;The tensile and compressive properties of the CFRP material parallel to and perpendicular to the fiber orientation were measured.Respectively,the tensile strength was 1218 MPa and 64 MPa,and the compressive strength was 884 MPa and 84 MPa.It was found that the CFRP material had obvious anisotropy.(2)The interfacial bonding properties of the adhesive(CFSR-A/B epoxy resin system)were studied,and the following conclusions were drawn:The effects of different steel surface treatment methods on the bonding property between steel plate and adhesive were studied,including sanding、pickling、phosphating and silane treatment.It was found that the bonding property between the steel plate and the adhesive after silane treatment was the best,and the bonding Strength was 25.3 MPa;The effect of temperature on the bonding property was studied.It was found that the bonding strength reached a peak near the glass transition temperature,which was 22.2 MPa;The influence of number of fiber layers and lap length on bonding property was studied.It was found that the longer the lap length,the higher the bonding ultimate load when the fiber layers were constant,but when the lap length exceeded the effective lap length,the load did not increase significantly;When the lap length was constant,the more the fiber layers were,the higher the ultimate load and bonding strength were.(3)The study on the energy absorption performance of the axial compression of the composite tubes was studied,and the following conclusions were drawn:The probability of the Euler bending deformation in the composite tubes was lower than that of the original tubes,and it had the effect of inducing progressive deformation.Through quasi-static axial crushing tests,the influence of four variables,such as fiber laying angle θ,fiber layer number,tube draw ratio and cross section shape,on energy absorption performance of composite tubes was studied:When θ was(0,90°),the total energy absorption of the composite tubes was 102.6%higher than that of the original tubes,the crush force efficiency was increased by 64.1%,and the specific energy absorption was increased by 70.7%;The crush force efficiency of the composite tubes increased with the increase of fiber layer number,but the specific energy absorption reached the peak value in three layers,up to 22.7 J/g.The increase of crush force efficiency of composite square tubes were greater than that of the circular tubes.By introducing variable thickness steel tubes,it was found that the energy absorption performance of the tubes was better than that of the original equal thickness steel tubes.At the same time,the composite variable thickness tubes were made,and the energy absorption performance of the tube was further enhanced compared with the original variable thickness steel tubes.The total energy absorption was increased by 52.3%,and the crush force efficiency was increased by 27.6%,The specific energy absorption was increased by 39.6%,up to 30.3 J/g.(4)The analytical models of axial compression of composite tubes were improved and verified.The average error between analytical results and experimental results of composite circular tubes and square tubes was 6.7%and 16.2%respectively.It had certain guiding significance.