ACOUSTIC WAVE TRANSMISSION OF MICROPOLAR PLATES

This study investigates the interaction of sound waves with expanded (EPS) polystyrene plates, which possess a microstructure composed of interacting grains. The Cosserat or micropolar theory of elasticity is recognized for its ability to account for the internal length scales inherent to materials with microstructure. This theory introduces additional independent rotational degrees of freedom, along with associated curvature strain and couple stress descriptors, enabling the continuum to support a diverse range of bulk waves. Therefore, we apply the Cosserat theory to model through-thickness vibrations of linear elastic EPS plates, aiming to reproduce the experimental response. Experiments were carried out to measure the transmission coefficient of such low density plates. With a comprehensive experimental setup including a loudspeaker, a microphone, and a data acquisition system, through-thickness frequencies were observed within the frequency range between 2 kHz and 70 kHz. The comparison between theoretical and experimental results allows for the identification and calibration of material parameters.