Research On Mode ? Fracture Performance Of Carbon Fiber/Steel Composite Structure

In recent years,with the development of composite materials,the mechanical properties of composite materials have been continuously improved,production costs have been reduced,and the performance of materials has been mature and stable.It has been widely used in the repair and reinforcement of steel structures.Carbon fiber-steel composite structure,as a bonded structure,has many mechanical advantages such as less deformation and uniform joint stress distribution due to its simple manufacturing process,which makes it widely used in automotive,civil engineering and other fields.It directly affects the reinforcing effect of the carbon fiber-steel composite structure,so how to improve the bonding performance is the research focus of scholars.In response to this problem,the surface roughening measures of surface grooving and sandblasting are adopted in this paper.Based on the bridging strengthening mechanism of short fibers,aramid chopped fibers and multi-wall carbon nanotube(MWCNT)fibers are used to bond the interface To carry out the reinforcement,the reinforcement mechanism research was carried out using the double cantilever beam(DCB)test and finite element simulation analysis.The main research contents are as follows:(1)For the bonding interface of the steel substrate after the groove treatment,the bonding layer is reinforced by adding aramid chopped fibers.Compared with the resin mixed curing agent bonding layer,the bonding layer after the aramid fiber film is reinforced Extreme load and critical energy release rate increased by 2.2% and 2.4% respectively.Due to the low roughness on the surface and groove of the grooved steel plate,type I fracture always occurs at the interface between the steel plate and the bonding layer,and the aramid fiber only strengthens Resin bonding layer and resin and carbon fiber interface layer.(2)In order to improve the interface bonding strength between the steel plate and the bonding layer,the surface of the steel plate is treated with sand blasting technology to improve the surface roughness of the steel plate,and the multi-wall carbon nanotube(MWCNT)fiber pretreatment technology is used to pass the nano The short fiber effectively strengthens the resin bonding layer.After the pretreatment coating,the extreme load and critical energy release rate of the bonding layer are increased by 22% and 23% respectively compared to the grooved surface.Type I fracture is mainly caused by the bonding layer Interlayer failure,meanwhile,the toughening effect of MWCNT is obvious,and the toughening mechanism of different interfaces is analyzed.(3)Because multi-walled carbon nanotubes are very prone to agglomeration,different concentrations of MWCNT will have different effects on the strength of the bonding layer at the blast interface.For this situation,three concentrations of MWCNT pretreatment solutions are studied in this paper The effect on the bonding layer shows that in the three concentrations of 0.3wt%,0.6wt%,and 1wt%,the higher the MWCNT concentration,the greater the number of carbon nanotubes that can be embedded in the surface of the blasted steel plate and the bonding layer.The interface strength and interlayer strength increase more significantly.(4)Based on the test results of the double cantilever beam(DCB),the necessary simulation parameters are obtained,and the ABAQUS finite element software is used to simulate the different bonding interfaces to obtain the load-displacement curves of the different bonding interfaces and compare them with the test results.Verify the validity of the simulation model.