603 Degradation of Materials by High Energy Atomic Oxygen

Abstract

The degradation of structural materials exposed in space is a new problem since various kinds of materials have been used for structures in low earth orbit (LEO). This paper presents an experiment of degradation on the ground and a simulation by the molecular dynamics (MD) method. In the experiment, atomic oxygen produced at a plasma torch is accelerated fluid-dynamically with working gas. Graphite, C/C (carbon/carbon) composite and Si-C. C. (silicon impregnated C/C composite) were used as the target materials. The mass loss per unit area depends strongly on the temperature of the material surface. The eroded surfaces of materials were observed with SEM (scanning electric microscope) and laser focus displacement meter. In case of C/C composite, the matrix region erodes substantially more than carbon fiber. The mass loss of Si-C. C. is less than that of corresponding C/C composite and only the C/C region erodes deeply with almost no erosion in Si and SiC regions. In order to investigate the degradation caused by high energy atomic oxygen, numerical simulation was performed for graphite using the MD method. The simulation model explains the influence of the impact energy of AO on the degradation of materials.