An Experimental Investigation into the Acoustic Characteristics of Fluid-filled Porous Structures—A Simplified Model of the Human Skull Cancellous Structure |
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Authors: | A K Ghosh A D Williams J M Zucker J L Mathews N Spinhirne |
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Institution: | (1) Mechanical Engineering, New Mexico Tech, Socorro, NM 87801, USA;(2) Air Force Research Laboratory, Space Vehicle Directorate, Kirtland AFB, NM 87117, USA;(3) High Explosive Physics Team, Los Alamos National Laboratory, Los Alamos, NM 87545, USA;(4) Materials Engineering, New Mexico Tech, Socorro, NM 87801, USA |
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Abstract: | In nature, shape and structure evolve from the struggle for better performance. Often, biological structures combine multiple
beneficial properties, making research into mimicking them very complex. Presented here is a summary of observations from
a series of experiments performed on a material that closely resembles the human skull bone’s cancellous structure under acoustic
loads. Transmission loss through flat and curved open-cell polyurethane foam samples is observed using air and water as the
two interstitial fluids. Reduction in strength and stiffness caused by porosity can be recovered partially by filling the
interstitial pores with a fluid. The test findings demonstrate the influence of the interstitial fluid on the mechanical characteristics
of a porous structure in a quantitative manner. It is also demonstrated that the transmission loss does not depend only on
the mass per unit area of the structure as predicted by acoustic mass law. Current tests also demonstrate that the transmission
loss is more sensitive to the interstitial fluid than the shape and support conditions of the structures. Test observations
thus support the concepts of “moisture-sensitivity of biological design” and the “law of hierarchy in natural design”. |
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Keywords: | Acoustic Fluid-filled Porous Skull Cancellous |
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