Home page > Research > Surface mechanics

Buckling driven delamination of thin films

by Jean-Yvon Faou - published on , updated on

Jean-Yvon Faou (PhD 2010-2013), Sergey Grachev, Etienne Barthel.

Figure 1 :SEM image of a telephone cord like blister

Thin film mechanics becomes more and more important as the complexity of the multilayers increases. When low adhesion and large residual compressive stress are combined, multilayers can be subject to buckling driven delamination. The biaxial state of the residual stress implies various morphologies among which the telephone cord like blister is the most observed (see Fig.1). Understanding the morphology of the blister could lead to direct measurement of the interfacial toughness.

We use the superlayer test (Multilayer_Adhesion) couple with a precise measurement of the stress state of the thin film to probe a wide range of interface. Controlled failure of the interface results in reproducible blisters in size and morphologies for a given interface.

In order to explain this morphology it is necessary to couple the mode mixity of the interfacial toughness (i.e mode II stronger than the mode I) and the buckling of the thin film. This coupling has been achieved by numerical simulations using finite elements and cohesive zone modelling. Propagation of the telephone cord blister obtained numerically is in accordance with experimental observation (see Fig. 2)

Figure 2: Numerical out of plane displacement (top) and experimental microscopy (down) views of the propagation of the telephone cord blister.

Collaborations

- Guillaume Parry - SIMAP, Institut National Polytechnique de Grenoble Domaine Universitaire, 1130 Rue de la Piscine, 38 402 St Martin d’Héres Cedex France

Publications

How Does Adhesion Induce the Formation of Telephone Cord Buckles? pdf HAL
J-Y. Faou, G. Parry, S. Grachev, E. Barthel, Phys. Rev. Lett. 108, 116102 (2012)

PhD Thesis

Mechanics of functionnal thin films : instabilities and adhesion HAL (pdf)
J-Y. Faou, (2013)