Accession Number:

ADA235695

Title:

Acoustic behavior of Negative Poisson's Ratio Materials

Descriptive Note:

Research and development rept.

Corporate Author:

DAVID TAYLOR RESEARCH CENTER BETHESDA MD SHIP MATERIALS ENGINEERING DEPT

Report Date:

1991-03-01

Pagination or Media Count:

28.0

Abstract:

Negative Poissons ratio NPR materials have been predicted to have unusual acoustic properties. To measure this effect, polyurethane foam was chosen to serve as a model system. Negative Poissons ratio materials were produced from open cell, reticulated polyurethane foams by heat setting the foam which was compressed in three dimensions to a volume smaller by the factor 3.7 than the original volume. Acoustic tests comparing the reflection properties of the unconverted, the NPR uncovered, and the NPR foam with an attached cover, and one with an unattached covering were made on foams with pore sizes ranging from 10 to 100 pores per linear inch. Uncovered NPR foams reflected less sound at all frequencies than the uncovered unconverted foam. Smaller pore size NPR foams absorbed sound more efficiently at frequencies above 630 than did those with larger pores, and those with covers were better sound absorbers in the frequency range 250 to 1000 Hz than the uncovered NPR foams. Unidirectional compression to 14th the original thickness reduced the Poissons ratio to zero and caused the foam to absorb nearly as well as did creation of the negative Poissons ratio.

Subject Categories:

  • Miscellaneous Materials
  • Acoustics

Distribution Statement:

APPROVED FOR PUBLIC RELEASE