Published online by Cambridge University Press: 10 December 2020
Liquid foams are, amongst other applications, used to mitigate shock waves. This aspect has received considerable attention at the macroscopic scale. However, the interaction between foam films and shock waves is still poorly understood and may be an important missing local information to build mitigation models. In this paper, we experimentally identify a new process leading to the foam film rupture, which dominates when the film thickness is sufficiently heterogeneous. Using a two-thickness film with a sharp and localised thickness gradient, we record the deformation of the interface between the thick and the thin parts. We observe the growth of an excess liquid area in the thin part and establish an analytical model and scaling laws which account for this phenomenon. Our results in this ideal configuration are consistent with actual rupture processes at stake in heterogeneous foam films.