Accession Number:

ADA179109

Title:

Material Damping Measurements of 2D Carbon-Carbon Composite Beams.

Descriptive Note:

Master's thesis,

Corporate Author:

AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH SCHOOL OF ENGINEERING

Personal Author(s):

Report Date:

1986-12-01

Pagination or Media Count:

117.0

Abstract:

Current work in thermal protective materials for space systems and advanced jet engines are investigating the use of an advanced carbon-carbon composite material ACCM to build critical components that must operate in very high temperature regimes. The potential use of ACCM in these applications must address the problems of vibration that might occur during system operations. Vibrations can cause severe performance degradations, if not controlled. One method of control, called passive damping, relies on the materials inherent damping characteristics. This study evaluates ACCMs damping characteristics, important to passive damping understanding. Modal analysis techniques using an impact hammer to excite sinuseidal free vibration were used to find the damping natural frequencies for 2-D ACCM beams. The logarithmic decrement technique was applied to the fundamental modes to verify the frequency and damping data derived by the modal analysis. Additionally, the logarithmic decrement technique was used to evaluate atmopheric drag influences on damping. It was shown that for small amplitudes, less than the beams thickness, the damping effects of atmospheric drag were minimized and considered negligible. Cantilevered beam specimens were studied for the first three modes in test conditions at room temperature and atmospheric pressure. Keywords material damping, carbon-carbon composites, modal analysis, vibration analysis.

Subject Categories:

  • Laminates and Composite Materials
  • Mechanics

Distribution Statement:

APPROVED FOR PUBLIC RELEASE