A Monte Carlo simulation technique to evaluate the effects of low-Earth-orbit atomic oxygen damage on thin films of polymeric materials is presented and discussed. The proposed method provides a tool that allows the evaluation of both the mean eroded thickness for exposed specimens and the degradation of their optical properties. Contrary to a full quantum mechanics approach, this method is based on a finite volume discretization of the bulk materials: Each simulation cell is characterized by a reaction probability in a standard exponential form. The reaction probability depends on the ratio between the total amount of kinetic energy transferred to the finite volume by the entering atomic flux and the internal pressure, that is, the cohesive energy of the simulation cell itself. The unknown parameters contained in the expression of the reaction probability are related to the mean eroded thickness and to the surface roughness rms through statistical considerations. The erosion yield is shown to be dependent on the cohesive energy density for polymeric materials: This observation provides a simple tool to estimate the reaction yields for standard hydrocarbon or fluoro-based polymers. The surface roughness rms is obtained from the mean optical properties of exposed materials via the scalar equations describing electromagnetic wave surface scattering. The results of Monte Carlo simulations have been compared to the data available for Kapton specimens flown both on the Long Duration Exposure Facility and Mir and retrieved after several months of exposition. The unknown parameters required for the simulations have been estimated by a nonlinear regression on experimental data. Good agreement has been obtained between the simulation results and the experimental data, both for the eroded thickness after exposure and for the mean optical transmittance of the specimens.
Atomic oxygen degradation of polymeric thin films in low earth orbit
Erosion dünner Polymerschichten durch atomaren Sauerstoff in niedrigen Erdumlaufbahnen
AIAA Journal ; 41 , 8 ; 1525-1534
2003
10 Seiten, 13 Bilder, 1 Tabelle, 20 Quellen
Article (Journal)
English
FLUID DYNAMICS - Atomic Oxygen Degradation of Polymeric Thin Films in Low Earth Orbit
Online Contents | 2003
|Low earth orbit atomic oxygen effects on surfaces
AIAA | 1984
|Atomic Oxygen Protection of Materials in Low Earth Orbit
NTIS | 2002
|