Experimental and theoretical evidence for the existence of broad forbidden gaps in the three-component composite

The influence of localized resonance on the properties of band-gaps of the two-dimensional periodic composite are analysed numerically and experimentally by comparing the two-component phononic crystal with the three-component one. The three-component composite which exhibits localized resonance in the elastically soft coating ring is composed of a square array of coated cylinders embedded in an epoxy resin. The coated cylinders consist of a steel inner core and a rubber coating, which has much smaller wave velocity and mass density than the matrix and the inner material. The measured transmission power of the three-component composite drops to the noise level in a broad ultrasonic frequency interval in contrast to the binary composite, which is in good agreement with the calculation using the finite element method.