Molecular Dynamics Simulation Study Of The Fracture Behavior Of Rubber Nanocomposites

Rubber nanocomposites(RNCs)have been widely used because of their superior mechanical,electrical and thermal properties than traditional composites.In the practical application,the tensile deformation of the material will lead to the fracture of rubber products,which will affect its service life seriously.Due to the complex structure of RNCs,it is difficult to quantitatively characterize the relationship between the structure and properties by traditional experimental methods.And molecular dynamics(MD)simulation has become an effective means to solve the problem.By adopting a coarse-grained MD simulation,we explore the relationship between the microstructure and the macroscopic properties of RNCs during the deforming process.The main work is as follows:(1)The influence of the filler grafting on the fracture behavior of RNCsWe have investigated the fracture properties of RNCs in details by particularly regulating the grafting density and the length of grafted chains of nanoparticles(NPs).The dispersion of the NPs,the stress-strain curve and the evolution process of the voids were mainly characterized.The results showed that with the increase of grafting density or the length of grafted chains,the dispersion of NPs became better,and the maximum stress and fracture energy first increased and then decreased,indicating that the optimal fracture property appeared at the mediate grafting density or the length of grafted chains.It was also found that the stress borne by the NPs was related to the number of chemical bonds between the grafted chains and NPs.The results also showed that the voids were more likely to be formed at the end of chains or on the surface of NPs.(2)The influence of crosslink density on the fracture behavior of RNCsA series of models with different crosslink density were built and the effect of crosslink density on the fracture properties of materials was investigated from the point of view of breaking bonds.The results showed that with the increase of the crosslink density the maximum tensile stress increased,but the elongation at break decreased.The higher the crosslink density,the more the total number of broken bonds,the faster the rate of broken bonds,and the more voids the system generated.And it turned out that the atoms of crosslink bonds are borne more stress than that of normal bonds,so they break more easily.In addition,it was found that the intermolecular slip and the break of chemical bonds would lead to the formation of voids.