Approche numerique et experimentale pour l'amelioration d'une methode de mesure de la force d'adherence de la glace par l'utilisation de films piezoelectriques

Researches undertaken in CIGELE and INGIVRE made it possible to develop a mechanical technique for measuring interfacial bonding strength of atmospheric ice, using PVDF film sensors which are embedded at the ice/substrate interface. The substrate is an aluminium beam on which PVDF piezoelectric sensors are bonded. The composite beam, formed by an aluminium beam and a deposited ice layer, is submitted to sinusoidal stress at the interface by an electromagnetic shaker on which one end of the beam is clamped. The ice layer is deposited artificially on the aluminium beam from sprayed supercooled water droplets in order to simulate atmospheric icing on structures. The preliminary results showed the validity of the method as well as the sensitivity of measurement with materials and surface qualities of the beams used.;However, the method suggested had not been calibrated. Moreover, as proposed, the method did not make it possible to check the influence of certain parameters like the speed of the vibration amplitude and the ice thickness. Under these conditions, automation as well as a calibration of the method was carried out.;The calibration of the method is based on the development of a finite elements model of the aluminium beam and PVDF film bonded to the surface of the latter. An 12% variation between the numerical results and those resulting from the experiments was obtained. This variation is acceptable since bonding of the PVDF film on the aluminium beam and joining of conducting wires on the PVDF film were not taken into account.;Moreover, thanks to the automation, the influence of the increase speed of the vibration amplitude could be carried out. The results obtained with three different values made it possible to show that measurements do not depend on the increase speed of the amplitude, but debonding time varies proportionally to this latter. That is however not the case of ice thickness which influences the value of measurement significantly. The experimental tests, carried out with three thicknesses for a constant increase speed of the vibration amplitude reveal a strong dependence of measurement to the ice thickness. Thus, the measured stress decreases with the increase thickness and is zero with an ice thickness that makes the neutral axis position to be at the ice/substrate interface.