L'émission acoustique appliquée à l'étude d’un feutre

Study and identification of the phenomenas intervening in the modification of the structure of a fiber-glass when it is deformed by acoustic emission associated with the treatment of the signal and pattern recognition

Département : Génie Mécanique, Université de Technologie de Compiègne

Abstract

The fiber-glass studied is porous material with a composite stucture used in various fields and has many applications.

Thermic and acoustic applications in building constructions, industry...

When this fiber-glass is deformed with a given rate of compression during a certain period of time, many physical phenomenas occur. The microscopic observation allowed us to determine the structure of this material (fig. I). Entangled fibers with no particular orientation, and with many connections : fibers-fibers, fiber-glue, aspects and dimensions of fibers, distribution of the glue on the surface of the fibers.

All these observations helped us to state that certain phenomenas exist. The results obtained by Isodata classification method concerning acoustic emission signals recorded during the differents compression experiments on two types of fibers-glass mentioned above enable us to confirm the existence of the following mechanisms : "Stick-slip” of fibers ; Rupture of fibers ; Vibration of fibers.

Practically all these phenomenas happen at the beginning of the compression of the fibers- glass. The phenomenon related to the stick-slip is always dominant.

For the Bl fiber-glass, the same mechanisms happen as for the ES fiber glass.

Because of the particular structure of this material, we may say that these mechanisms play an important role during the decompression of the material in order to come back to its initial thickeness.

Thus, the condition of the surface and the physico-chemical characteristics of the fibers, the distribution of the glue can have a considerable influence on the existence and apparition of these different mechanisms.