This paper describes an evaluation of the capability of a mechanical impedance instrument, for detecting delamination defects in aluminium honeycomb structures. The resonant frequency was found to decrease as the centre of a defect was approached. The defects have been found to be accurately represented by a model for a vibrating plate, which is rigidly clamped at its edges. It was also possible to use resonant frequency to determine the size of the defects in the specimens used in this paper. An irregularly shaped defect showed that the rate of drop in resonant frequency across an extremity of the defect was affected by the radius at the extremity and the proximity to the main central area of the defect. An important result was that an ellipsoidal shaped defect would be sized as a circular defect of diameter equal to the minor diameter of the ellipse. Also a boron skinned honeycomb was found to behave similarly to a glass fibre skinned honeycomb.
DETERMINATION OF THE SIZE AND DEPTH OF DEFECTS IN MULTILAYER PCM HONEYCOMB STRUCTURES BASED ON THE MECHANICAL IMPEDANCE VALUE
