Accession Number : ADP004686

Title :   Experimental Measurement of Passive Material and Structural Damping for Flexible Space Structures,

Corporate Author : MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF AERONAUTICS AND ASTRONAUTICS

Personal Author(s) : Crawley,E. F. ; Sarver,G. L. ; Mohr,D. G.

Report Date : NOV 1984

Pagination or Media Count : 13

Abstract : 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. Graphite/epoxy 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 graphite/epoxy 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.

Descriptors :   *DAMPING, *COMPOSITE MATERIALS, *MEASUREMENT, EXPERIMENTAL DATA, ALUMINUM, FLEXIBLE STRUCTURES

Distribution Statement : APPROVED FOR PUBLIC RELEASE