Characterization of the adhesion quality in an aeronautical assembly by acoustic microscopy

This work deals with the characterization of the adhesion quality and of the adhesive film properties in Titanium/Epoxy adhesive film/3D Composite aeronautical assemblies.Due to the thickness of the adhesive film in the different samples, between 80 m and 200 m, the study is carried out with a scanning acoustic microscope (SAM) in pulse-echo mode, at high frequencies (20 and 50 MHz).The difficulties expected and that are challenged are due both to the acoustic impedance contrast between the materials and to the high frequency of the study, which should render the reflected echo at the Epoxy film/Composite undetectable or very low.These conditions mean that the experiment must be carried out carefully and with high accuracy.Nevertheless, the observation of the low amplitude reflected echo at the adhesive film/Composite interface in the different samples was possible thanks to the good signal-to-noise ratio (SNR) of the experimental set up instrumentation.The properties of the adhesive film are determined using the A-scan method with a planar transducer.Moreover, SAM images are obtained using a focused transducer, confirming the adhesion quantification and providing a fast estimation of the adhesive film thickness.