ULTRASONIC BAND-GAP IN A PERIODIC 2-DIMENSIONAL COMPOSITE

The first experimentally observed ultrasonic full band gap in periodic bidimensional composites for the longitudinal wave mode is described in this Letter, The structure consists of an aluminum alloy plate with a square periodic arrangement of cylindrical holes filled with mercur y. No propagation wave exists at the frequency range between 1000-1120 kHz irrespective of the measurement direction. The experiment was per formed by means of an ultrasonic transmission technique, and a measure ment of the position dependence of the acoustic amplitude was also per formed. [S0031-9007(97)05225-3].