Experimental Measurement of Passive Material and Structural Damping for Flexible Space Structures,
MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF AERONAUTICS AND ASTRONAUTICS
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The results of an experimental effort to both characterize material damping and enhance structural damping are presented. In order to determine material damping in metallic and fibrous composite materials, a unique facility has been constructed in which transient decay measurements were made in free fall in a vacuum. Specimens were simultaneously excited and lofted with a tuned spring-cocked launcher. Damping data on the free-free mode was obtained by bonding strain gauges to the specimen and connecting them by fine wires to a terminal also in free fall. Graphiteepoxy laminates tested were undirectional 0 deg. and or 45 deg. Symmetric, under environmental conditions of room temperature and near zero moisture content. Aluminum damping data agrees exactly with previous studies, as to stress and frequency dependence. The material damping in graphiteepoxy was found to be largely independent of frequency and stress level. In order to increase the passive damping level, it is possible to deliberately introduce dry frictional damping into a flexible structure.