Experimental Measurement of Material Damping for Space Structures in Simulated Zero-G
Abstract
An experimental apparatus for measuring the material damping properties of a beam specimen is described. The apparatus, called Tuneable Excitation Launch Mechanism (TELM) measures the free decay of free-free beams launched into free-fall in a vacuum. Aluminum 2024-T3 specimens are tested with results following the Zener model for specimens with a fundamental free-free frequency above the relaxation frequency. However, specimens with a fundamental free-free frequency below the relaxation frequency show a high degree of stress dependence. Frequency range was 17 Hz to 358 Hz and stress range was 0.5 KSI to 17 KSI. Graphite/epoxy ASl/3501-6 laminates were also tested. For (o) sub 8 laminates, material daming ratio of approximately .000555 was found for frequencies varying from 45 Hz to 237 Hz. The damping was neither stress on frequency dependent. For (90 sub 8) laminates, the damping ratio ranged from . 0055 to .0066 as frequency ranged from 42 Hz to 143 Hz. Damping ratios for (90 sub 8) specimens with graphite fibers, magnesium matrix, and either titanium or magnesium foil were also tested. Damping ratios ranged from .00039 to .00099 depending upon the lay up, frequency, and possibly the stress range involved.
Document Details
- Document Type
- Technical Report
- Publication Date
- Dec 01, 1983
- Accession Number
- ADA139215
Entities
People
- Raymond L. Sheen
Organizations
- Air Force Institute of Technology