[SY-E14] Buckling delamination of ductile thin films on rigid substrates
Thin film coatings submitted to high compressive stresses may experience a simultaneous buckling and delamination phenomenon called "blistering". The mechanism of formation and propagation of blisters in the form of straight wrinkles and circular blisters has been extensively studied in the literature considering a linear elastic behaviour of the film [1,2] . The recent developments in numerical calculations allowed a better understanding of the mechanism of formation and propagation of complex buckling geometries including wavy buckles. In particular, the relationship between the mode mixity dependent interfacial toughness and the morphology of the wavy buckles has been elucidated [3].
However, up-to-date, the response of ductile thin films deposited on rigid substrates remains an open issue. For instance, it has been evidenced experimentally [4] that circular blisters in ductile thin films exhibit larger folding angles at their base compared to the elastic model predictions. In addition, recent experimental observations of 400nm gold films deposited on silicon wafers showed straight buckles with higher deflections compared to the elastic model. These differences in morphology are thought to originate from the elastic-plastic response of the film but the governing features need to be clarified.
In this work, we are interested in the observation and characterization of buckling structures observed on gold films deposited on silicon substrates. In this context, we carried out a Finite Elements simulations with a model that accounts for isotropic yielding and the non-linearity of the film. A mode mixity dependent cohesive zone model is used to describe the thin film/substrate interface. This model allowed us to highlight the effect of plasticity on the equilibrium profiles resulting from elastic-plastic blistering, for both straight and circular blisters morphologies. In particular, a stabilizing effect of the circular blister form, which has been observed experimentally, has been demonstrated through calculation.
[1] Hutchinson et al., Adv. in Appl. Mech. 29 (1992) 63.
[2] Hutchinson et al. Acta Metallurgica Materialia, 40 (1992) 295
[3] Faou et al., J. Mech. Phys. Sol., 75 (2015) 93.
[4] Coupeau et al., Thin Solid Films 469 (2004) 221.
However, up-to-date, the response of ductile thin films deposited on rigid substrates remains an open issue. For instance, it has been evidenced experimentally [4] that circular blisters in ductile thin films exhibit larger folding angles at their base compared to the elastic model predictions. In addition, recent experimental observations of 400nm gold films deposited on silicon wafers showed straight buckles with higher deflections compared to the elastic model. These differences in morphology are thought to originate from the elastic-plastic response of the film but the governing features need to be clarified.
In this work, we are interested in the observation and characterization of buckling structures observed on gold films deposited on silicon substrates. In this context, we carried out a Finite Elements simulations with a model that accounts for isotropic yielding and the non-linearity of the film. A mode mixity dependent cohesive zone model is used to describe the thin film/substrate interface. This model allowed us to highlight the effect of plasticity on the equilibrium profiles resulting from elastic-plastic blistering, for both straight and circular blisters morphologies. In particular, a stabilizing effect of the circular blister form, which has been observed experimentally, has been demonstrated through calculation.
[1] Hutchinson et al., Adv. in Appl. Mech. 29 (1992) 63.
[2] Hutchinson et al. Acta Metallurgica Materialia, 40 (1992) 295
[3] Faou et al., J. Mech. Phys. Sol., 75 (2015) 93.
[4] Coupeau et al., Thin Solid Films 469 (2004) 221.