Interface delamination of layered media: acoustic spectroscopy and modal analysis.

We have developed a method of resonance ultrasound spectroscopy (RUS) to study the acoustic spectral response to interface delamination in a triple-layered rectangular parallelepiped [Al(aluminum)/polymer/Al]. Combination of laser-Doppler interferometry and the Rayleigh-Ritz approximation affected mode identification in the measured resonance spectrum. Point-contact RUS is capable of sensing a minute delamination (1.5% of total area). Modal analysis using a number of resonance modes can deduce the delamination area and location in the interface. Not only screening but also defect characterization is possible. At the same time, some resonance modes are totally insensitive to an interface imperfection. These modes are found to have virtually no strain energy arising from the bonding layer.