Experimentally Characterizing the Dynamics of 0.5m+ Diameter Doubly Curved Shells Made From Thin Films

1 ABSTRACT The purpose of this paper is to present the results of a series of measurements made to experimentally determine the dynamics of doubly curved very thin film shells. Results for in-air tests of 0.5 m and 1.0m diameter 51micron thick shells are presented first, followed by details of in-vacuum and in-nitrogen tests of the 1.0m diameter sample. The general trends expected from theoretical predictions were observed but the exact values were not. First modes were about a factor of 2 lower than that predicted by simple closed form theory. That being said, fundamental frequencies of 200 and 105 Hz for 0.5 and 1m diameter structures that are only 51 microns thick is quite impressive. In all cases the fundamental membrane modes were higher than that of their support structure. Based on the results of the in-vacuum and in-nitrogen tests, the 1.0m diameter shell was determined to be sensitive to aerodynamic mass loading but no clear conclusions could be drawn with respect to potential hygroscopic moisture outgassing induced tensioning effects.