The membrane resonance method of non-destructive testing

Abstract

The physical basis of the membrane resonance method of non-destructive testing has been investigated both theoretically and experimentally. The method involves exciting the structure and monitoring the response at the same point, and can be used to detect the presence of delaminations or disbonds at that location. Its advantage over ultrasonic testing is that no couplant is required between the transducer used and the structure, so the technique is convenient for use in the field. The method is most sensitive if the membrane resonance of the layer above the defect is in the frequency range of the excitation used, so it is desirable to employ wide-band exciation. It has been shown that the sensitivity of the method falls with increasing defect depth, but its performance at defect depths above about 4 mm is superior to that of the commonly used mechanical impedance and coin-tap tests. The method therefore seems to be an attractive possibility for the detection of delaminations in composite materials and disbonds in adhesive joints, and warrants further investigation.