Damping of Flexural Waves in Plates by Homogeneous Fibrous Material

Abstract

The present study treats the interaction between porous blankets and the reactive near fields associated with flexural waves on plates. For the frequency range below the coincidence frequency it is shown that the damping produced by this interaction may be considerable. The amount of damping obtained is found to depend on such properties of the fibrous material as porosity, flow resistance, and structure factor. In the present studies, two cases were considered: one in which an infinitely thick fibrous blanket was near but not touching the plate, and the other in which an infinitely thick fibrous blanket was in direct contact with the surface of the plate. The results of numerical calculations performed by a digital computer (programmed to handle complex numbers) are shown to be in reasonably good agreement with experimental data, (This work was sponsored in part by the U, S. Air Force, Wright Air Development Division.)