title: Detachment of stretched viscoelastic fibrils.
abstract: New experimental results are presented about the final stage of failure of soft viscoelastic adhesives. A microscopic view of the detachment of the adhesive shows that after cavity growth and expansion, well adhered soft adhesives form a network of fibrils connected to expanded contacting feet which fail via a sliding mechanism, sensitive to interfacial shear stresses rather than by a fracture mechanism as sometimes suggested in earlier work. A mechanical model of this stretching and sliding failure phenomenon is presented which treats the fibril as a nonlinear elastic or viscoelastic rod and the foot as an elastic layer subject to a friction force proportional to the local displacement rate. The force on the stretched rod drives the sliding of the foot against the substrate. The main experimental parameter controlling the failure strain and stress during the sliding process is identified by the model as the normalized probe pull speed, which also depends on the magnitude of the friction and PSA modulus. In addition, the material properties, viscoelasticity and finite extensibility of the polymer chains, are shown to have an important effect on both the details of the sliding process and the ultimate failure strain and stress.
authors.affiliation: Laboratoire de Physico-Chimie des Polymères et Milieux Dispersés, UMR7615 ESPCI-CNRS-UPMC, 10 Rue Vauquelin, 75231, Paris Cédex 05, France.
authors.forename: N J
authors.initials: NJ
authors.lastname: Glassmaker
authors.forename: C Y
authors.initials: CY
authors.lastname: Hui
authors.forename: T
authors.initials: T
authors.lastname: Yamaguchi
authors.forename: C
authors.initials: C
authors.lastname: Creton