Effect of defects to the band-gaps generation

Effect of defects to the band-gaps generation in sonic composites is investigated in this paper. Acoustic scatterers are composed by piezoceramic hollow spheres of functionally graded materials. Defects are vacancies or foreign interstitial atoms which are supported by the interfaces between the hollow spheres and the matrix. The presence of defects in sonic composites is related to the generation of localized modes in the vicinity of the point defect with a significant evanescent behavior of the waves outside the defect point. As result, the full band-gap is wider than in the case of no defects. (© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)