Without glue, it sticks?

Using an electro-adhesion device, we are characterizing for the first time the adhesion between a film and a substrate obtained without an intermediate layer of adhesive. The latter’s properties are generally poorly controlled, making adhesion studies extremely difficult. For this purpose, ultrasonic waves are generated and detected by lasers to probe the interface without contact. The results obtained using this non-destructive method clearly demonstrate the sensitivity of surface acoustic waves to only electrostatically-induced variations in film adhesion.

This study concerns material adhesion, which is often crucial to the reliability of coating technologies. Specifically, the quality of contact between a polyvinyl chloride film and an aluminum substrate is assessed non-destructively by Laser Ultrasonics. Generally, a layer of adhesive is used between the film and the substrate, but its properties (thickness, homogeneity, etc.) are difficult to control and complicate adhesion characterization. For this reason, an original electro-adhesion device (Figure 1) is used to vary the film’s adhesion by applying electrostatic fields of different intensities, thus dispensing with the need for an adhesive layer (Figure 2). In addition, the propagation of surface acoustic waves in the structure is sensitive to adhesion via the dispersion of phase velocities. Considering the effect of normal and tangential stiffnesses at the interface, dispersion curves for Rayleigh modes were determined. These were also obtained using the finite element method (Figures 3 and 4). Experimentally, these guided waves are generated by a frequency-doubled Nd:YAG laser and detected by a Mach-Zehnder heterodyne interferometer. Analysis of the dispersion curves of different modes has enabled us to distinguish each level of adhesion. These innovative results pave the way for future Laser Ultrasonics studies to better quantify the phenomenon of electro-adhesion for various materials.


Find out more:

Mustapha Baher, Meriem Chrifi Alaoui, Frédéric Jenot, Mohammadi Ouaftouh, Marc Duquennoy, « Characterization of electro-adhesion using surface waves generated and detected by Laser-Ultrasonics », NDT&E International, Volume 147, 2024, 103191, ISSN 0963-8695, https://doi.org/10.1016/j.ndteint.2024.103191

Figure 1: (a) Electro-adhesion device, (b) Field source used, (c) Experimental setup


Figure 2: Adhesion of a PVC film to an aluminum substrate for two electrostatic fields of increasing intensity. Applied voltage 3.6 kV (a) and 3.8 kV (b)


Figure 3: Rayleigh modes determined by finite elements and theoretical dispersion curves (black lines) for perfect film/substrate contact


Figure 4: Finite element simulation of the normal displacement of acoustic waves generated in the film/substrate structure