The Micropolar Elastic Waves Propagation In Layer Medium Characteristics Research

The micropolar elastic theory is used for describing the deformation of themedium containing granular particles. This theory considers the microrotation andmicrostretching of the granular particle. In recent years, due to the wide applicationand rapid development of the composite materials, wave-absorbing material andstrengthen or hybrid particle materials make the micropolar elastic theory become veryimportant. The research of wave-absorbing materials is the most significant. Becausethe stealth and electromagnetic compatibility (EMC) technology become more andmore important, the effection of electromagnetic wave absorption material is veryoutstanding. It becomes a modern military in the magic weapon of the electroniccounter and a "secret weapon". The engineering application of electromagnetic waveabsorption material includes mainly in the stealth technology for aircraft and ships andthe performance improving of the plane and safety protection, and so on.In this paper, based on the micropolar fluid theory and the micropolar solidelasticity theory, the micropolar elastic wave’s propagation characteristices are studiedwhile it traveling through the sandwich type medium (such as micropolar elastic plateor micropolar fluid). Using the basic equation of micropolar fluid and the micropolarplane wave, the linear equations of longitudinal displacement wave and coupled waveamplitude ratio are obtained. These equations are solved by Gaussian EliminationMethod. Using the numerical results, the curves of reflection coefficient ortransmission coefficient with the change of incident angle are plotted for differentincident frequency or different material parameter. From these analyses, the mainconclusions can be written as follows:1. The reflection or transmission wave’s amplitude ratio relates to the incidentangle, the frequency of the incident wave and the media material properties. With thechange of incident angle, the reflection coefficient and transmission coefficient of longitudinal displacement wave or coupled wave is variational.2. For the longitudinal displacement wave or coupled wave, while it passingthrough the micropolar elastic plate submerged in micropolar fluid, the propagationcharacteristics are studied. For incident longitudinal displacement wave, there is amaximum value in the curve of reflection coefficient or transmission coefficient ofcoupled wave. And the reflection coefficient or transmission coefficient of longitudinaldisplacement wave decreases with incident angle. For incident coupling wave, thereare two extremum and zero value in variation curves of the reflection of longitudinaldisplacement wave and the transmission coefficient. At the same time, transmissioncoefficient presents wave phenomenon.3. For the longitudinal displacement wave or coupled wave, while it passingthrough the micropolar fluid layer in micropolar solid, the propagation characteristicsare also studied. For incident longitudinal displacement wave, the reflection coefficientor transmission coefficient are small for bigger incident angle. For incident couplingwave, there are two extremum and zero value in variation curves of the reflection oflongitudinal displacement wave and the transmission coefficient. There is oneminmum value in curve of reflection coefficient of coupling wave. And threre ismaxmum value in curve of transmission coefficient of coupling wave or of reflectioncoefficient of longitudinal displacement wave.This research results is the theoretical basis for studying absorbing material in thefield of aircraft, ships and aircraft, and so on.