Accession Number : ADA307123
Title : Vibrational Characteristics of Sandwich Panels in a Reduced-Pressure Environment,
Corporate Author : NATIONAL AERONAUTICS AND SPACE ADMINISTRATION HAMPTON VA LANGLEY RESEARCH CEN TER
Personal Author(s) : Powell, Clemans A., Jr. ; Stevens, David G.
PDF Url : ADA307123
Report Date : AUG 1966
Pagination or Media Count : 20
Abstract : 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.
Descriptors : *VIBRATION, *SPACECRAFT, *COMPOSITE MATERIALS, *DAMPING, *SANDWICH PANELS, SHEAR PROPERTIES, ACOUSTIC WAVES, RESONANT FREQUENCY, ALUMINUM, POLYURETHANE RESINS, RIGIDITY, HONEYCOMB STRUCTURES, EXPANDED PLASTICS.
Subject Categories : Laminates and Composite Materials
Distribution Statement : APPROVED FOR PUBLIC RELEASE