Numerical Simulation Of Fractal Aggregation And Dispersion Behavior Of Nanoparticle Aggregates

The addition of nano-particles into polymer matrix or metallic matrix is generally used in field of nanocomposites to improve physical and mechanical performance of composite materials.And to a large extent,dispersion effectiveness of those microscopic particles determines the performance of the final products.However,nano-particles,featuring high surface energy,easy aggregation and poor compatibility with most matrix,are far hard to disperse evenly.As a result,to advance dispersion effectiveness of nano-particles is of great significance of research on the area of nanoparitcle material processing.Currently,it is hard to measure precisely the dynamic information,including displacement,speed and contact force during processing nano-particles,and hard to assess the impact that aggregation structure has on dispersion effectiveness.With the development of discrete element method,scholars begin to conduct researches on dispersion of aggregation.In the previous studies,aggregates in fractal structure which are similar to the authentic one are formed through the aggregation model achieving the simulation of dispersion behavior of nano-particle aggregates in flow field.But,due to the lower performance of the model,neither the occlusion relation among particles in flow field could be reflected by adopting fluid drag force model dispersedly,nor its principle could be revealed with the simple post-processing results.Therefore,the further study on dispersion behavior of aggregation in fractal structure is expected to reveal the dispersion principle of how aggregation processes in the real flow field.In this paper,modified fluid drag force model based on discrete element method and modified aggregation algorithms are applied to the software DEMix 3D,which could simulate the process of aggregation and dispersion of fractal aggregates in flow field.The result showed that: DLA aggregates had denser structure and smaller branching structure than DLCA aggregates;algorithmic efficiency was improved under algorithms of dynamic-release,localsearch and optimized processing of the overlapped particles;chain and cluster structure existed during dispersion while fracture was more likely to appear in chain structure,whose distribution density of catenoid force chains determined the dispersion efficiency and effect;there was a power function relationship between the weighted number of particles in the final fragment and flow field intensity.