Non-destructive testing of composites using long waves

A new technique for detecting faults in composite panels has been developed based on measurements of the local phase velocity of low frequency flexural waves. Broadband excitation is used so the method includes source configurations and software to reduce the effect of the reverberant field. An X-Y scanning version has been built employing non-contact methods and a handheld version based on a note book computer has also been constructed. The method has been used on multi-ply panels to determine stiffness matrix elements and lay-up errors. Delaminations and core damage in honeycomb sandwich panels have also been detected via scattering of the waves.