We perform traction experiments on viscous liquids highly confined between
parallel plates, a geometry known as the probe-tack test in the adhesion
community. Direct observation during the experiment coupled to force
measurement shows the existence of several mechanisms for releasing the stress.
Bubble nucleation and instantaneous growth had been observed in a previous
work. Upon increasing further the traction velocity or the viscosity, the
bubble growth is progressively delayed. At high velocities, cracks at the
interface between the plate and the liquid appear before the bubbles have grown
to their full size. Bubbles and cracks are thus observed concomitantly. At even
higher velocities, cracks develop fully so early that the bubbles are not even
visible. We present a theoretical model that describes these regimes, using a
Maxwell fluid as a model for the actual fluid, a highly viscous silicon oil. We
present the resulting phase diagramme for the different force peak regimes. The
predictions are compatible with the data. Our results show that in addition to
cavitation, interfacial cracks are encountered in a probe-tack traction test
with viscoelastic, \emph{liquid} materials and not solely with viscoelastic
solids like adhesives.Comment: 44 page
