LOCAL PHASE-VELOCITY MEASUREMENTS IN PLATES

A method for measuring local phase velocities in panels, in the range 5-50 kHz, in the presence of a strongly reverberant field, and within 10 cm of structural discontinuities such as ribs, is described. The me thod gives a resolution of 1-2% and a 2-3% reproduceability. Measureme nts of the phase velocity as a function of direction for a three-ply a nd a 12-ply carbon-fibre composite plate are presented. Local values o f the elastic properties of individual laminae in the plates, as a fun ction of direction, are calculated from the phase velocities. Small va riations in the lay-up angles of some of the laminae are also detected . (C) 1995 Academic Press Limited