| Rubber tires usually work under periodic loads.Long-term use will cause serious internal heating and fatigue damage in the rubber tires.The safety problems caused by rubber fatigue damage are often very serious.In particular,the thermal conductivity of rubber materials is low,and the internal hysteresis heat generation is difficult to release into the environment,which further leads to a decrease in fatigue performance.In order to improve the fatigue resistance of natural rubber,it is considered to improve the thermal conductivity of natural rubber to export the hysteresis heat generation from the rubber matrix to the environment,thereby improving the fatigue performance of natural rubber composites.At the same time,due to the long fatigue test cycle,consider using the finite element method to introduce the thermo-mechanical coupling equation to improve the accuracy of the rubber fatigue life prediction.In this study,natural rubber is selected as the rubber matrix.First,a finite element analysis method that can predict fatigue life is established.At the same time,a ball milling method is used to prepare graphene,and then graphene and aluminum oxide are used as thermally conductive fillers to compound with natural rubber.The focus is on the effect of thermal conductivity of rubber composite materials on fatigue performance.The first part of the thesis mainly uses the finite element method to realize the fatigue life prediction of the rubber composite material,and introduces the superplastic constitutive equation and the hysteresis heat generation model into the fatigue life prediction,realizing the fatigue life prediction of the rubber composite material.The results show that the introduction of thermal-mechanical coupling analysis can greatly improve the accuracy of fatigue life prediction.Compared with the non-thermal-mechanical coupling analysis,the error value is reduced from 213.9%to 13.9%in consideration of the influence of temperature on viscoelasticity.In the second part,the concentration of the graphene aqueous dispersion was optimized by adjusting the milling time,the initial concentration of graphite,the concentration of sodium methylene naphthalene sulfonate(NNO)and the concentration of cetyltrimethylammonium bromide(CTAB).The GE structure was characterized by atomic force microscope,Raman spectroscopy,X-ray electron diffraction,etc.The results showed that he graphene dispersion can reach a maximum concentration of about 3.3 g/L giving 10 h the milling time,100 g/L for the initial graphite concentration,1 g/L for the NNO concentration and 0.05 g/L for the CTAB concentration.Meanwhile,the thickness of the graphene sheet is about 1.6 nm,and the two-dimensional lateral size is about 500 nm.The third part mainly studies the effects of GE reinforcement and the combination of GE and Al2O3 on the fatigue performance of natural rubber.The results show that with the increase of the graphene fraction,the tensile strength,100%tensile strength,300%tensile strength,tear strength,and thermal conductivity of the rubber composite material are significantly enhanced.When the graphene fraction is at 7 phr,the thermal conductivity of the GE/NR composite material reached 0.262 W/m·K,indicating that the prepared graphene not only has a certain reinforcing performance,but also can effectively improve the thermal conductivity of the natural rubber composite material.Combining GE and Al2O3,it is found that as the number of GE increases,the 100%tensile strength,300%tensile strength and thermal conductivity of the rubber composite material increase.Comparing its fatigue performance,the results show that when the graphene content is 5 phr,the fatigue life of the rubber nanocomposite is best.The main reason is that when the graphene content is less than 5 phr,the fatigue life of the rubber composite is subject to heat conduction.When the graphene fraction is higher than 5 phr,the fatigue life of the rubber composite is mainly affected by heat generation. |
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