Accession Number:

ADA139215

Title:

Experimental Measurement of Material Damping for Space Structures in Simulated Zero-G

Descriptive Note:

Master's thesis,

Corporate Author:

AIR FORCE INST OF TECH WRIGHT-PATTERSONAFB OH

Personal Author(s):

Report Date:

1983-12-01

Pagination or Media Count:

124.0

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. Graphiteepoxy ASl3501-6 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.

Subject Categories:

  • Laminates and Composite Materials
  • Metallurgy and Metallography
  • Mechanics
  • Unmanned Spacecraft

Distribution Statement:

APPROVED FOR PUBLIC RELEASE