Study On Uniaxial Fatigue And Micro-Properties Of Cerium Oxide Filled Vulcanized Natural Rubber During Thermal Aging

The vulcanized natural rubber?NR?products usually work under the condition of periodic and complicated load.Because they are easy to be hardened under high temperature for a long time and lead to premature failure of the materials,the effect of the thermal aging of the vulcanized NR on the fatigue performance needs to be taken into account.Many studies have shown that filling cerium oxide?CeO₂?in rubber can effectively improve the fatigue properties of vulcanized NR,so it is of great practical significance to study the thermal aging fatigue properties of vulcanized NR filled with CeO₂?NR/CeO₂?.The thermal aging tests of NR/CeO₂ and unfilled vulcanized NR specimens were carried out at 60?,80?and 100?for 24 h and 72 h,respectively,and the tensile tests were carried out on them by oven accelerated aging method.The results showed that the samples were CeO₂-filled for 24 h and unfilled vulcanized NR specimens for 72 h respectively.CeO₂-filled improves the comprehensive mechanical properties of thermal aging vulcanizates and plays a reinforcing role.The effect of CeO₂-filled on the uniaxial fatigue properties of NR the strain amplitude of 0-125%,0-150%and 0-175%was studied.The results show that the fatigue stress of the two materials increases with the increase of aging temperature or aging time.The larger strain can lead to the increase of the stress and the decrease of the fatigue life,and the axial stress of the thermal aging rubber is obviously enhanced by CeO₂-filled.After aging at 60?and 80?for 24 hours,the fatigue life of the material was increased by CeO₂-filled.The results show that when the temperature is lower than 80?,the CeO₂-filled has a positive effect on the fatigue life of vulcanized NR under normal deformation condition.The microstructure of thermal aging materials shows that CeO₂ has a good dispersion in the matrix,improves the internal network structure of rubber,and enhances the interaction force between molecular chains of rubber.With the increasing of strain amplitude and aging temperature,the cross-section of the two kinds of rubber develops to brittle fracture.When the aging temperature is lower than 80?,the toughness of NR/CeO₂ cross-section is more excellent.The crosslinking density of NR/CeO₂ was higher than that of unfilled NR.The crosslinking density of NR/CeO₂ increased with the increase of aging temperature.The crosslinking density of NR/CeO₂ at 60?and 80?for 24 hours was higher than that of unfilled.The fatigue life of NR/CeO₂ was higher than that of unfilled NR at different strain amplitudes.The NR/CeO₂ had good thermal stability.The finite element analysis of thermal aging NR/CeO₂ was carried out.The constitutive model and the corresponding material parameters were determined by combining the constitutive model and the corresponding material parameters.The stress solution corresponding to the thermal aging fatigue test was calculated by simulation.