定点滞空飛行試験後の膜材残留強度及び試験法評価

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The Low Altitude Stationary Flight Test was conducted at Taiki-cho, Hokkaido in 2004 as a part of the Stratospheric Platform development. High strength and lightweight envelope materials such as Vectran and Zylon were applied to the test vehicle and they have proven to have sufficient performances in the flight test. However, these materials are known to deteriorate during operation and measures to prevent deterioration caused by exposure to sunlight and ultraviolet rays are issues for their long life operation. Accordingly, data on their deterioration characteristics were obtained and the materials were applied to the Low Altitude Stationary Flight Test Vehicle after confirming durability. Nevertheless, the deterioration characteristics under actual operation are still very important data for the coming development. After the flight test, the envelope materials were cut off from the test vehicle and tested with spare materials and monitor materials placed on the top of the hull during the flight test. Test parameters were tensile strength at room and high temperatures, tear strength at room temperature, and creep strength at high temperature, all of which are important in the design. Before starting the test, test methods were investigated and the rigorous methods specified by JIS and FED-STD were adopted. The tensile strengths of the spare materials were found to be about 20% higher than the development test results. It was possible to obtain their intrinsic material properties by selection of the proper test method. In other words conservative data were used in the design of the test vehicle. The Vectran envelope material showed a 10% reduction in tensile strength after the flight test. The Zylon envelope material, whose layer composition differs from that being developed for a stratospheric platform, showed a large reduction. The Zylon envelope material, which was developed for a stratospheric platform, showed almost no deterioration. This result made it clear that improper selection of the protective layer induces deterioration. Regarding the creep strength of the joint specimen, the test results after the flight test showed longer life than those of the development test. The specimen production method in the development test seems inappropriate. The Zylon envelope material which showed very short creep life in the development test did not rupture after 1,000 hours. Thus Zylon has demonstrated excellent creep strength. Valuable data on envelope materials after the flight test were obtained. It became clear that proper test method selection is very important for such high strength materials.
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定点滞空飛行試験後の膜材残留強度及び試験法評価

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