Molecular bonding aided by dissipative inter-layers

Interface toughening in multilayered systems through compliant dissipative interlayers

“…The properties of the interlayer heavily affect the interface toughness evolution with ht/R0. While the dependence of Gss/G0 on ht/R0 has already been reported for the monolayer case (Martiny et al, 2012;Tvergaard and Hutchinson, 1994) and, to some extent, for the plastic interlayer case (Bertholet et al, 2007;Wei and Hutchinson, 1999), the fact that an elastic interlayer can induce a significant toughening is a new finding. The next subsections aim at describing the evolution of the interface toughness with ht/R0 for the three studied cases, as well as its dependence on the investigated parameters.…”

“…While not shown there, it has been found that increasing hil/R0 has no effect when /Eil is equal to 0.05. These trends were already described and analyzed by (Wei and Hutchinson, 1999) and (Bertholet et al, 2007) The effect of Es/Et and σc/ on the interface toughness evolution with ht/R0 for all three cases (monolayer, elastic interlayer and elastoplastic interlayer) was investigated but is not described here. In summary, it showed that increasing these two parameters always leads to an increase of the interface toughness:…”

“…Such methods are obviously not adapted for non-transparent substrates as used here. Thus, an indirect procedure was defined based on the out-of-plane displacement profile uy(x) of the specimen, following the earlier work of (Navarro et al, 2013), (Bertholet et al, 2007) and (Olbrechts et al, 2006). The relationship between uy(x) and a can be determined analytically by comparing one arm of the wedge opening test to a beam deformed by an imposed displacement at a distance a from the crack tip.…”

“…The role of this interlayer is only to deform plastically during the crack propagation at the interface between the thin layer and the substrate, thus improving the overall toughness. (Bertholet et al, 2007) exclusively investigated this kind of configuration for a thin layer and a substrate made of an identical elastic material and a ductile interlayer with elastic properties identical to those of the other layers. For such case, the interface gets tougher as the thickness of the thin layer and of the interlayer decreases and increases, respectively.…”

Kinetics of low temperature direct copper–copper bonding

“…This technique was initially developed for brittle materials fracture. Since copper layers are ductile, the measured toughness contains an additional plasticity term (Bertholet et al 2007). In this work, qualitative comparisons are possible because the thickness of copper films and therefore at first order the mechanical properties of all studied samples are considered equivalent.…”