| The dispersion effectiveness of nano-sized particles in polymer matrix has a direct impact on the comprehensive properties of polymer nanocomposites. The nano-sized particles with high surface energy will condensation form aggregates under Van der Waals forces and electrostatic force. Thus, improving the dispersion uniformity of filled nanoparticles in a polymer matrix is a very important project for the polymer processing. It is difficult to accurately measure displacement, speed and contact force of particles in processing by experimental methods. And it is difficult to assess the effect of aggregate structure on the dispersion of particles.With the development of discrete element method(DEM), Many scholars begin to study the dispersion of aggregate using the discrete element method. But in the previous studies, the aggregates are usually simple structure or compact structure, it is difference from the structure of those aggregates, which formed by random movement. Thus, the results of previous studies incompletely show the dispersion characteristics of the aggregates. In addition, the dispersion mechanism of aggregates was not revealed. With the development and improvement of computer simulation technology of fractal aggregation, the structure of aggregate generated by fractal aggregation model is very similar to real aggregate. Therefore, research on dispersion behavior of fractal aggregate in flow field would contribute to reveal the dispersion mechanism of aggregate in the real processing flow field.In this thesis, computer simulation technology of particle fractal aggregation and discrete element method are combined. A Particles Aggregate and Disperse software(PA&D) is developed in Visual Studio 2010 software by C++ programming language. Visualization of particle motion behavior is realized by OpenGL. PA&D are applied to simulate the process of particles aggregates and the dispersion process of fractal aggregates in flow field. The results show that:(1) under the same system conditions, fractal dimension of aggregates would be improved with the increase number of particles,(2) different values of diffusivity exponent ? will make different effects on the diffusion coefficient, and then lead to different aggregation result,(3) the complex force chain network with the strong and weak force chains interwined is formed in aggregates, dispersion mode is determined by the evolution of force chain network in aggregates during dispersion process,(4) the f?w ? of DLCA aggregate would reduce in power-law relationship with the increase of the intensity of flow field,(5) under the same intensity of flow field, the dispersion effectiveness of elongation flow is higher than shear flow. |
