Soutenance d'Hélène Piot-Durand
| When |
Oct 29, 2021
from 02:00 to 04:00 |
|---|---|
| Where | Salle Condorcet (1 place de l'école) |
| Contact Name | Hélène Piot-Durand |
| Attendees |
Hélène Piot-Durand |
| Add event to calendar |
vCal
iCal
|
Simultaneously controlling the adhesion strength and release dynamics of adhesives is important in many industrial fields. The most common approach involves chemical modifications of the adhesive (polymeric) layer and/or the substrate interface. In this thesis, we propose an original approach involving modifications of the physical properties of the substrate, such as its topography and its elasticity. We carried out a detailed experimental study, where a pressure sensitive adhesive tape is peeled off from a transparent substrate, at a constant imposed speed, over a wide range of velocities (from a few μm/s to several m/s). We prepare our substrates with different materials : UPVC films (adhesive tape backing), glass, PMMA, PDMS layers of varying elastic modulus and thickness. These surfaces are textured by micro-milling or photolithography, by making grooves transverse to the peeling direction, a few μm in depth and width, regularly spaced a few μm apart. We visualize directly the detachment process, while measuring the force required to peel the adhesive tape. At high velocity and on smooth and rigid substrate, the detachment front usually follows a jerky propagation, alterning periodically between slow and fast phases, which is accompagnied by a drop in adhesion energy. We show that the combined deformation of the substrate and the adhesive increases the adhesion force and affects the peeling dynamics, by reducing the speed threshold for the appearance of the stick-slip instability. Moreover, we also show the possibility of controlling this instability through the texture of the substrate, by shifting its threshold velocity or by forcing the amplitude of fast micro-slips.