Molecular Dynamics Simulation And Analysis Of Microscopic Damage Mechanism In Particulate Reinforced Composites

Macroscopic properties of materials are determined by their microstructure. With further research on composite materials, the research on particle reinforced composites has been extended to the nano-scale currently. The researchers found that the reinforcement on the one hand improved the mechanical properties of stiffness and strength of materials, on the other hand led to a significant decrease in the mechanical properties of materials, such as fracture toughness and fatigue properties. For particulate reinforced composites, the effects of both positive and negative depend on the interfacial crack, reinforcement crack, matrix crack and other microstructure. Therefore, in order to better understand and take advantage of particulate reinforced composites, based on molecular dynamics method and open source LAMMPS, matrix cracks of particulate reinforced composites have been studied in UBUNTU system. Open source VMD is used as a post-processor and to display the dynamic changes of crack propagation in the loading process.The main contents are as follows:1. This paper describes the basic concepts and methods of molecular dynamics which are comprised of time integration algorithm, the initial and boundary conditions, the time step, parallel computing methods and so on. Especially for the three basic theories of molecular dynamic, the basic equations of molecular dynamics, potential function and an ensemble are reviewed. To understand and master these important theories could lay a solid foundation for molecular dynamics simulation.2. Through the establishment of the matrix model containing micro-crack and an accurate selection of the potential function, in this paper, the dynamic process of crack propagation of matrix copper was carried out by molecular dynamic simulation. Combined with the extension mechanism of crack tip, the destruction process of copper matrix from micro-crack of the initial state to complete failure of materials is described. 3. Through the establishment of the copper matrix model containing modeⅠ crack, the dynamic process of mode Ⅰ crack propagation of matrix copper was investigated in molecular dynamic simulation. The crack tip position on the±45°slope where is most likely to generate slip and dislocation is validated. As the stress concentration of crack tip and crack propagation instability, it led to the phenomenon of crack deflection during the process of crack propagation. Furthermore, compared with the characteristics of crack propagation of mode I under different load speeds, in the event of the same displacement, the smaller load speed, the more dislocations and slips to display in the loading process of the matrix.