Computational Study for Delamination Detection in Fiber-Metal Laminates Using Lamb Wave Propagation

Delamination is known as the most important damage in fiber-metal laminates (FMLs). The purpose of this study was to assess the ability of guided Lamb waves for the detection of delamination in FMLs through numerical models developed using the finite element method (FEM). The developed FEM models consisted of an FML sample with [Al / ۹۰ / Al / ۹۰ / Al] layup having a delamination damage of ۱۰, ۱۵ and ۲۰ mm diameter between different layers, an ultrasonic actuator and several sensors. The anti-symmetric Lamb wave with a frequency of ۷۰ kHz and symmetric Lamb wave with a frequency of ۴۰۰ kHz were propagated on the sample using the actuator. The sensors were then used to obtain the induced wave characteristics, including the displacement phase and amplitude at different locations along the propagation direction. The Lamb wave velocity was obtained using the measured wave characteristics. Using the change of velocity in the delamination region, the sensitivity of the anti-symmetric and symmetric Lamb waves to the damage and the diameter of delamination were determined.