Erosion of POSS-polyimide films under hypervelocity impact and atomic oxygen: The role of mechanical properties at elevated temperatures

Low Earth orbital debris impacts oil the external Surfaces of satellites have increased dramatically in recent years. Polyimides are used as the outer layer of thermal control insulation blankets. covering most of the external spacecraft surfaces that are exposed to the space environment. A recently developed material, named polyhedral oligomeric silsesquioxane (POSS)-polyimide. shows significant enhancement in withstanding the space environment. In this work. the combined effect of ground-simulated hypervelocity space debris impacts and atomic oxygen (AO) on the erosion of POSS-containing polyimide films was investigated. During Such hypervelocity impacts, elevated temperatures, on the order of hundreds degrees, arc Formed. A laser-driven flyer system was used to accelerate aluminum flyers to impact velocities of up to 3 km s(-1). The impacted films were exposed to an oxygen RF plasma environment, simulating the effect of AO in the low Earth orbit. Impacted polyimide films exposed to AO revealed synergistic erosion effect, while impacted POSS-containing samples showed improved erosion resistance. The increased erosion rate of the impacted polyimide film is explained by formation of residual stresses that affect the oxidation mainly by increasing the diffusivity of oxygen into the subsurface layers. Mechanical properties of the POSS-containing samples performed at 450 degrees C and fractographic examination supports the above hypothesis. (C) 2008 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.