The Propagation Properties Of Elastic Waves At The Interface Of One-dimensional Periodic Composites

In recent years, a new type of periodic composites proposed has aroused wide attention and research from domestic and foreign scholars. The composites constructed by periodic and elastic media own band gap properties of elastic waves. That are to say, elastic waves can't spread in the composites when frequency is within a certain range. Because of the band gap properties, the periodic composites have a wide application in vibration isolation, attenuation, noise reduction and so on. Under dynamic loads, the elastic waves would inevitably encounter with the interface of composites and have a complex interaction on it. This paper, using the plane wave expansion method, first calculated and analyzed the band structures of the omni-directional elastic waves in three kinds of periodic composites, which were constructed by lead and expoxy, aluminum and expoxy, steel and expoxy. Then, we discussed some factors, including the propagation direction, the filling fraction and component of composites, impacted to the band structures and the width of band gap. Sequently, we analyzed the propagation properties of anti-plane shear waves at the interface making use of the band structures, and discussed some factors, such as the frequency of elastic waves, the component of composites, the filling fraction, the half-space different media, incident angle and so on, affecting the reflectional coefficient and refractional coefficient which characterized the energy distribution of the refiectional waves and the refractional waves. It came to the conclusions as follows(1) When the elastic waves spread along direction of transmission cycle, the width of band gap are maximum and the frequency under the edge of band gap is minimum.(2) Compared to the matrix, the larger the material properties of scatter are, the bigger the width of the band gap.(3) When the filling fraction increases gradually, the width of band gap first increases then decreases. The smaller and larger filling fraction is not easy to generate the bandgap.(4) The frequency of elastic waves has an effect on the energy distribution. When thefrequency is low, the impact to the propagation properties at the interface is minimal, and the refractional energy is less than the refiectional energy; When the frequency is high, the influence to the propagation properties at the interface is obvious.As the directional band gap comes, some directional waves can't propagate in the periodic composites, leading in curve discontinuities. While some directional waves can enter the periodic composites, the higher the frequency is, the smaller the coefficient is.(5) Compared to the matrix, the greater the resistance of the scatter is, the bigger the refractional coefficient is and the smaller the reflectional coefficient is(6) When the filling fraction is equal to 0.5, the refractional coefficient is minimal at low frequency; the vast majority is in band gap at high frequency and the refractional coefficient is zero.(7) The greater the impedance of the uniform medium is, the bigger the refractional coefficient is and the smaller the reflectional coefficient is.In practional application, identifying the main source of elastic waves direction and frequency range,we want to achieve the best results through the design and adjustment of the the system's position, the component of composites, the filling fraction, the uniform medium and so on.