Observation and model of highly ordered wavy cracks due to coupling of in-plane stress and interface debonding in silica thin films

Abstract

Highly ordered wavy cracks are observed in silica films deposited on crystalline Si wafer. The wavy crack path is interpreted in terms of the coupling of the in-plane film crack and the interface debonding. A model based on the analyzing of the crack path and the stress evolution is proposed to describe the propagation of the wavy cracks. A scaling relationship between the wavelength ͑͒ and amplitude ͑A͒ is found ͑ ϳ A ͒ and the scaling factor is determined to be = 0.47Ϯ 0.01.

Fracture path in brittle thin sheets: a unifying review on tearing

“…Spiral patterns are sometimes observed in the fracture of strained film bonded to a substrate: converging spirals are reported in drying layer (Argon 1959;Dillard et al 1994;Leung et al 2001;Néda et al 2002;Xiaa and Hutchinson 2000) when the material debonds from the substrate. Diverging fracturing spirals are sometimes observed (Lebental 2007;Meyer et al 2004;Sendova and Willi 2003;Wan et al 2009) in similar systems, where stresses are due to the film deposition process. However in both cases the spirals seem to be archimedian, with the radius decreasing or increasing by a specific characteristic distance at each turn.…”

Self-Replicating Cracks: A Collaborative Fracture Mode in Thin Films

“…We indeed obtain W 1 32h and W 2 25h, which is large in comparison with the interaction length of the usual channel cracks (on the order of h). The robustness of these patterns observed with very different types of coatings and deposition methods, such as sol-gel [1,[13][14][15], magneton sputtering [17], or evaporation [16] suggests that their characteristic width is independent from both loading conditions or material properties and only depends on the thickness of the film. This robust size selection clearly indicates that these patterns are different from other spiral or oscillating fracture paths observed in systems involving thermal gradients [20], drying fronts [21] or tearing with a blunt object [22].…”

“…Indeed, similar crescent alleys or spiral patterns have been mentioned in different areas of material science [1,[13][14][15][16][17][18][19]. However, the corresponding fracture mechanism remains mysterious.…”

A new failure mechanism in thin film by collaborative fracture and delamination: Interacting duos of cracks

“…Recent studies have put in evidence a novel mode of failure of thin films, involving the collaboration between fracture and delamination [24]. This mode leads to various patterns displaying a characteristic width curiously robust [19,20,21,22,23]. The present study focuses on a novel fracture pattern that is crucial for the understanding of fracture propagation in the presence of delamination: a pair of parallel cracks connected by a straight delamination front that propagates simultaneously and leads to the detachment of strips with a steady width.…”