Vibrational Characteristics of Sandwich Panels in a Reduced-Pressure Environment

An investigation was conducted to determine the vibrational characteristics of sandwich panels over a wide range of environmental pressure or density. Natural frequencies and damping of panels having aluminum honeycomb and polyurethane foam cores were determined for several modes of vibration over a...

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Bibliographic Details
Main Authors: Powell, Clemans A., Jr, Stevens, David G
Format: Report
Language:English
Subjects:
ACOUSTIC WAVES
ALUMINUM
COMPOSITE MATERIALS
DAMPING
EXPANDED PLASTICS
HONEYCOMB STRUCTURES
Laminates and Composite Materials
Manned Spacecraft
POLYURETHANE RESINS
RESONANT FREQUENCY
RIGIDITY
SANDWICH PANELS
SHEAR PROPERTIES
SPACECRAFT
Unmanned Spacecraft
VIBRATION
VIBRATION DAMPING
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Summary:An investigation was conducted to determine the vibrational characteristics of sandwich panels over a wide range of environmental pressure or density. Natural frequencies and damping of panels having aluminum honeycomb and polyurethane foam cores were determined for several modes of vibration over a pressure range from 760 torr (1 atmosphere) to 10-6 torr. Results indicate that no significant changes in either natural frequency or damping occur between a pressure of 1 torr and 10-6 torr. A decrease in pressure from 1 atmosphere to 1 torr produces an increase in frequency from 2 to 10 percent due to "apparent mass" effects and possible increases in panel thickness and shear rigidity. Furthermore, a corresponding decrease in pressure results in a linear decrease in damping due to a reduction in acoustic radiation. The change in frequency and damping with pressure is dependent upon the mode shape of the panel.