• Korean Journal of Optics and Photonics
• /
• v.13 no.1
• /
• pp.1-8
• /
• 2002

Optical payloads for earth-observation satellites become bigger as the required resolution becomes finer. For example, the diameter of the primary mirror of IKONOS, which has ground sampling distances of 1m/4m in panchromatic/multi spectral bands, is about 700mm. As the size of optical payload becomes bigger, the light-weighting of the mirrors becomes more significant. This paper presents the FEM results of the following four mirror types of 300 m diameter under gravity release and temperature changes: flat back mirror, single arch mirror, double arch mirror, and honeycomb sandwich mirror. Furthermore, this paper extends the FEM results to larger mirrors up to the diameter of 1m based on a general scaling law and Valenete\`s equation.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.38 no.9
• /
• pp.862-868
• /
• 2010

Development of a small scale aircraft has been carried out for the BASA(Bilateral Aviation Safety Agreement) program in Korea. This aircraft adopted all the composite structures for environmental friendly by low fuel consumption due to its lightness behavior. However the composite structure has s disadvantage which is very weak against impact due to foreign object damages. Therefore the aim of this study is focusing on the damage evaluation and repair techniques of the aircraft composite structure. The damages of composite laminates including the carbon/epoxy UD laminate and the carbon/epoxy fabric face sheets-honeycomb core sandwich laminate were simulated by a drop weight type impact test equipment and the damaged specimen were repaired using the external patch repair method after removing damaged area. The compressive strength test and analysis results after repairing the impact damaged specimens were compared with the compressive strength test and analysis results of undamaged specimens and impact damaged specimens. Finally, the strength recovery capability by repairing were investigated.