Carbon Material Erosion In Hypersonic Flowby Molecular Dynamics Simulation

The erosion damage of materials under hypersonic flow is a key problem in the engineering of hypersonic aircraft. In this paper, molecular dynamics method is used to study the erosion process of graphite in hypersonic oxygen flow. The main work of the thesis includes:The interaction processes of the double-layered and triple-layered graphite with hypersonic oxygen flow are studied using molecular dynamics method based on Reax FF potential. The surface layer of graphite is combined with oxygen atoms under the continuing impact of the hypersonic oxygen flow. Then some of the combined oxygen atoms and carbon atoms dissociate from the graphite in the form of CO2. In addition, it shows that the temperature of the surface layer rises slowly in the condition of the triple-layered graphite case.Molecular dynamics method based on REBO potential is used to study the interaction processes of multi-layer graphite in hypersonic oxygen flow. Modify the REBO potential that contains only Carbon and Hydrogen atoms by adding Oxygen atom in LAMMPS. The effect of oxidation on the graphite’s equivalent in-plane stiffness is studied. The results show that the breakup of the multi-layer graphite under the erosion of the hypersonic oxygen flow occurs layer by layer. The destruction of graphite relatively delay if the graphite has more layers. The Double-Vacancy defect accelerates the process of heating and damage of the surface graphite. The Single-Vacancy defect affects less than the Double-Vacancy defect. The influence of the Stone-Wales defect on the erosion process can be ignored. In addition, the adsorption of oxygen on the graphite has little effect on its equivalent in-plane stiffness. However oxygen combination in the defects reduces the equivalent in-plane stiffness of the graphite.The calculation scale of molecular dynamics method for graphite erosion problems is discussed. Molecular dynamics method based on REBO potential is used to simulate a system that contains 33516 carbon atoms and 12000 oxygen atoms for 200 ps on a single core with the time step 1fs. The total time cost is about eight hours. It is much more efficient than the Reax FF force field. In addition, the phenomenon of the surface graphite is showed from defects formation, defects extension to complete damage. At the same time, in the process of simulation, the temperature of the surface graphite and the change of the system potential energy are analyzed.