Non-destructive evaluation of coating thickness using guided waves

• Guided waves are used for coating thickness estimations.
• The characterization technique proposed can be used on any type of substrate.
• Using low frequency, S0 mode is a good candidate.
• Experimental precision within 10 μm can be obtained.
• The technique proposed is insensitive to surface periodicity or roughness.

For thin coating thicknesses, techniques for thickness characterization requires a high level of precision. On composite structures, actual bulk wave methods can be impaired by the presence of a periodic metallic mesh on its surface, thus reducing their performance. In this paper, a technique based on guided waves is proposed for coating thickness characterization. This method relies on the interpolation of the linear behavior of the S0 mode at low frequency with regard to thin coating thicknesses. It is demonstrated numerically and experimentally that coating thickness can be estimated within 10 μm of the actual coating thickness.