Peeling behavior of thin viscoelastic tapes

Viscoelasticity, frictionandgeometry:whichistheirroleingoverningthebehavior of adhesive systems? Despite the long standingeffort onthese issues, capturingandmodelingdissipativephenomenaandnon-linearities inherent inreal processesisatoughchallenge, leavingseveralquestionsandproblemsunresolved. This thesis explores someof theseparticular aspects insoft contactmechanics withaprimaryemphasisonpeelingprocesses. Inthefirstpart, anoverviewof thepeelingmechanismisprovidedwhere themost important resultsandmodelsarediscussed. Mainconceptsof linearviscoelasticityarealsogiventodefine themathematical framework foranalyzingviscoelasticpeeling. Weaddress the singlepeelingof thinviscoelastictapes inthecaseof stuckandfrictional sliding interfaces.WhileaKendall-likebehavior ispredictedintheabsenceof slippage, whenconsidering frictional dissipation inthemodel sensibledifferencesemerge. Higherpeelingforcesareobservedatlowpeelinganglesandthesystemtoughness becomesvelocity-dependentinagreementwithexperimentalobservationandphenomenologicalmodels.WealsoinvestigatetheV-peelingconfigurationaddressing thenonsteadypropagationwhichoccurs as the effect of time-dependentmaterialbehaviorandsystemgeometryvariation.Nonmonotonicevolutionofpeeling quantitiesresultsfromthecontinuouscreepoftapeduringthedetachmentprocess whichcanalsoarrestforparticularcombinationsofinitialparametersandloading conditions. Interestingly,forimpactloadingconditionsanenhancementofpeelresistanceispredictedsuggestingthatviscoelasticitycouldbecrucialforthesuperior adhesiveperformanceofnaturalpeelingsystems. Inthe lastpart,wediscussan experimentalstudyonslidingcontactbetweenasphericalglassrobeandaPDMS substratecarriedviaanadhocdevicewhichallowsforthemeasureofsurfaceinplanedisplacements.Weconsistentlyobserveacontactareareductionandashape asymmetryasapossibleeffectofgeometricalandmaterialnon-linearitiesarisingin thetensile/compressivezoneatthetrailingandleadingedge, respectively,where highlevelsofstrainareachievedandnormal-tangentialuncouplingpredictedfrom linear-elasticity isbroken. Mechanical confinementalso leads toamodification of couplingbehaviorwithrespect to infinitecontactconditions, suggestingthat geometricalaspectsarepivotaltobetterunderstandingfrictionaladhesivecontact.