Ultrasonic guided wave method for evaluating the interface bonding property of ultra-thin two-layer composites

An ultrasonic guided wave method suitable for evaluating the interfacial bonding property of the ultra-thin two-layer composite was presented. The ultra-thin here means that the thickness of the layer is only a fraction of the ultrasonic wavelength so that the echoes from the front and back surfaces cannot be separated in the time domain. The interfacial bonding condition of the ultra-thin two-layer composites was estimated by using the dispersion properties of the ultrasonic guided waves propagating through it. The reasons for evaluation error of the parameters and the sensitivity of the method were analyzed. In experimental study the technique was employed to characterize the interface properties of the ultra-thin aluminum/brass composite with thickness down to 10 percent of the ultrasonic wavelength with a pair of broadband 2 MHz longitudinal wave transducers. It is observed that the agreement between the nominal value and the estimation is excellent.