Electronic Devices and Materials Group, Aerospace Research and Development Directorate, Japan Aerospace Exploration Agency (JAXA)
Division of Mechanical and Space Engineering, Graduate School of Engineering, Hokkaido University
The mechanical properties of polyimide (PI) films, which were exposed to the space environment in the SM/SEED (Service Module/Space Environment Exposure Device) experiment, were evaluated with tensile tests. Additionally, PI films irradiated by atomic oxygen (AO), ultraviolet, and electron beam using ground facilities were similarly evaluated. Through comparison of these PI films' results, it was revealed that AO was the main space environmental factor degrading the mechanical properties of the PI films. Tensile strength and elongation of the PI films reduced concomitantly with increased AO fluence (F(sub AO)). The PI films expressed rough surfaces because of AO erosion and ruptured from the rough surfaces. In addition, their surface roughness increased as the F(sub AO) increased. These facts suggest that the degradation of mechanical properties is attributable to the increase in surface roughness. The mechanical properties of ITO (Indium Tin Oxide)-coated PI films (ITO/PI films) irradiated by AO were also evaluated. Generally, ITO/PI films have a high durability to AO erosion because ITO coating blocks AO. Therefore, ITO/PI film surfaces remain smooth even after AO irradiation. Tensile strength and elongation of the ITO/PI films, however, reduced with FAO increasing, marking higher degradation than the case of non-coated PI films. The AO-irradiated ITO/PI films have many undercut cavities at defect sites of their ITO coatings and ruptured from the undercut cavities. The undercut cavity developed as F(sub AO) increased, leading to significant degradation of the mechanical properties. The relationship between F(sub AO) and tensile strength in PI and ITO/PI films was predicted with fracture mechanics. The predicted results almost corresponded with the experimental results. The evaluation indicated that fracture mechanics is an effective approach for strength deterioration analysis of PI films exposed to the space environment.
内容記述
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内容記述（英）
Physical characteristics: Original contains color illustrations
宇宙環境曝露によるポリイミドフィルムの機械特性劣化とその予測法
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