Inspectability of interfaces between composite and metallic layers using ultrasonic interface waves

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The interface between an anisotropic composite material and a metallic material is inspected non-destructively for disbonded regions using ultrasonic guided waves. The material properties of the composite and metal have been tailored to demonstrate their effect on inspectability. The material properties have been designed to be either favorable or unfavorable to the existence of propagating Stoneley waves. Stoneley waves can exist because the layer thicknesses are large enough compared to the wavelength to be considered half-spaces. The existence of Stoneley waves between generally anisotropic materials depends on the elastic constants and densities in a complicated way. The range of material properties that allow Stoneley waves is small; however, when the vertically polarized shear wave speeds are similar in the two materials, the existence of Stoneley waves is generally possible. If the conditions do not strictly allow Stoneley waves, other interface waves can still exist such as leaky waves. Disbonds are inserted into the materials before bonding and are inspected using interface waves. Sensitivity to disbonds is determined and thus inspectability is demonstrated for cases that are favorable and unfavorable to Stoneley waves. Both numerical and physical experimental results are shown.