Aircraft De-Icing Using Time-Reversed Guided Waves

The passage of elastic waves in layered structures gives rise to interfacial stresses that can cause delamination. While usually undesirable, this can be exploited to remove unwanted accretions from a substrate, such as ice from an aircraft wing. High-amplitude transient waves, such as those induced by electro-expulsive de-icing systems, have proved effective, although their range is limited in part due to pulses spreading out with propagation distance from the actuator. In this paper, the phenomenon of wave dispersion that causes this effect is exploited through time reversibility to focus waves both spatially and temporally and hence amplify the peak response at a chosen position. Harmonic finite element analysis is first undertaken to determine the wave bearing characteristics of a simplified representation of a wing leading edge. Transient analysis is then performed on the structure with an attached ice layer to focus disturbances of bandwidths up to 50 kHz at different chosen points. The amplitude of the peak shear stress between the ice and substrate is bandwidth dependent and predicted to be up to 30 times higher than due to a comparable pulse input. Predicted peak accelerations are successfully validated experimentally for a limited bandwidth of 10 kHz.