Local defect resonance of a through-thickness crack

In recent years, Local Defect Resonance (LDR) has generated much interest in development and applications of new resonant acoustic modes for non-destructive testing (NDT) and imaging of planar defects in composite materials. The studies and applications are focused at LDR in composites where the most common defects are delaminations and impacts. This paper considers the mechanism of development and the attributes of LDR for through-thickness cracks in plates. The experiments validate that the LDR is caused by the resonance of the edge waves propagating along the crack faces. The edge wave resonance features weak field decay away from the crack, partial as well as high-order LDR and provides clear opportunities for applications in NDT techniques based on acoustic activation of damage.