Research On Fatigue Properties Of Nanofillers/Rubber Composites In Different Dimensions

Rubber products such as rubber shock absorbers and tires are usually working under cyclic loading.After long time using,rubber products and their loaders will be damaged and fatigue will occur.The safety problems caused by rubber fatigue are often serious.As the wear resistance and strength of the rubber are low,it can not meet the requirements of many industries.It is usually required to add filler to reinforce the rubber.The amount of filler,the geometric size,and the dispersion in the rubber matrix will affect the fatigue properties of the rubber.In this paper,the rubber matrix is selected as natural rubber,the filler is chosen spherical carbon black,one-dimension nanofiller carbon nanotube,and two-dimensional nanofiller oxidize graphene.The effect of filler content,size effect and composite effect on the fatigue property of natural rubber is studied.In the first part of the thesis,a new two-dimensional graphene oxide was prepared by Hummers method.The structure of GO was characterized by FTIR,Raman,XPS,XRD and AFM.The results showed that the interlayer spacing of GO was larger than graphite.There are abundant polar oxygen-containing functional groups such as carboxyl group,epoxy group and hydroxyl group on the surface of the layer;the thickness of the graphene oxide sheet is about 1 nm,and the two-dimensional transverse dimension is about 2?m.The second part mainly studies the influence of the contents and dimension of reinforcing filler on the fatigue performance of natural rubber in pure shear state.The results showed that CB,CNT and GO were well dispersed in NR matrix.The mechanical properties of NR composites increased significantly with the increase of each filler fraction.Then the influence of the dimension of the filler on the fatigue resistance of the natural rubber composite material was investigated.For the improvement of the crack propagation property of the natural rubber composite material,a small number of portions of the tubular filler CNT and the layer structure of GO could be a considerable amount of CB at normal temperature.The study of crack propagation properties of rubber composites at different temperatures showed that the advantages of CNT and GO at high temperature weakened and the effect of interfacial action between the filler and the rubber matrix on the fatigue properties became more important.Through the evolution of the crack tip morphology,it is found that when the CB is added to the natural rubber matrix,the evolution of the crack tip morphology is less than that of CNT and GO.At the same time,the section morphology after fatigue is wavy,and the wavelength will become longer with the increase of temperature.The third part mainly studies the effect of composite effect of reinforcing filler on fatigue resistance of NR composites.It was found that CB and GO interacted with each other in NR matrix.With the increase of graphene oxide content,the binding strength and mechanical properties of NR composites are also increasing.It is found that the crack growth rate of CB/NR rubber material was decreased at different tear energies after the addition graphene oxide The study of crack propagation characteristics at different temperatures shows that compared with single filler,the advantage of adding composite filler is very obvious in the whole temperature range.Even at 100 C,it still has a low crack propagation rate.It is mainly attributed to the stronger network structure of graphite oxide and carbon black in the rubber matrix,which restricts the movement ability of the rubber chain and makes the crack tip form more abundant.Through the exploration of the evolution of the crack tip morphology,a mechanism is proposed to influence the crack propagation characteristics of the rubber composite,and the evolution of the crack tip morphology will affect the crack growth rate of the rubber composite.The study of crack growth rate after different fatigue degrees found that with the increase of fatigue times,the crack growth rate of GO/CB/NR rubber composite undergoes a process of decreasing and then increasing.