5A-2. High Frequency Propagation Measurements in Microstructured Solids

High frequency ultrasonic wave propagation in an immersed porous aluminium sheet is modelled and the results verified by experiment using focused broadband 50, 100 and 175 MHz waves. For colinear (pores extending from face to face of the sheet) samples the microstructure facilitates transmission at angles beyond 35°, which is far greater than the critical angles for a homogeneous solid, and at a constant velocity.