Linear and nonlinear acoustic parameters measurements in plates with various moisture contents

Variation of the moisture content is known to modify many of the mechanical properties of solids. For this reason, the estimation of the absorbed quantity of water is a subject of growing interest in characterization of materials. In this work, the water content in phenolic resin plates, placed under variable relative moisture conditions, is investigated through linear and nonlinear acoustic parameter measurements. Linear measurements are performed using an insertion/substitution spectroscopy technique. Nonlinear measurements consist of an evaluation of the phase modulation obtained by a collinear interaction between a high frequency tone burst and a low frequency wave. Results show that many of the studied parameters have a good sensitivity to the absorbed water content.