The fracture path in an elastic thin sheet, when generated by large bending seems to be highly reproducible. Why ?
We may observe the robustness of tearing in many situations and everyday:
Simplest tearing … 
Trouser test and anisotropy…
Spiraling torn path is a generic feature…
We found several occurences of torn sheets cut along diverging “logarithmic spirals“. This is because these spirals, having no scale, preserve angles.
One of them occurs when a cone perforates a brittle sheet into a number of crack smaller than 4. In that case, the spirals are intertwined [See our article].
Another situation leading to spiral spath is when one pulls on a tab starting with a specific initial geometry [See our patent]
When fracture and delamination collaborate
In a thin coating, residual stresses may lead to usual disordered fracture patterns (mud cracks, glaze on pottery), but here cracks propagate together with a debonding front, and very robust patterns are produced.
fracture in real time of a crescent alley
fracture in real time of a spiral
See also movies of a competition between a duo of cracks and a following crack. [see our article Self-replicating cracks : A collaborative fracture mode in thin films Phys. Rev. Lett 113, 085502. (2014)]This letter was selected as a PRL Editors’ Suggestion and featured in Physics by Michael Schirber and Physics Today by Sung Chang.
See also press release in Le Monde by David Larousserie, Physics Today by Sung Chang, New Scientist by Jacob Aron (and the corresponding movie), in Inside Science by Gabriel Popkin and (in French) by ESPCI ParisTech, SVI, CNRS ) by Jean-Michel Courty, (INSIS CNRS), UPMC, (in German) in Welt der Physik by David Vogel.
The article is featured by Sarah Zhang on Gizmodo, by Douglas Natelson (Rice University) on his condensed matter blog, on physics4me, Auracaria de Chile, in Thai, in Tamil, on social networks by Physics Today on FB and (in Russian) Ñ‡ on VK
- Peeling/Skinning : the frustrating pinch-off When trying to peel off an adhesive film or skinning a fruit, the film often tears and pinches-off. We only get a finite-size pointy strip.
Why this finite time singularity ? The answer is in the fold joining the two cracks. [see our article ]
Collaboration with E.Hamm et E.Cerda (USACH, Chili) and P.M.Reis (MIT)
- Oscillating crack in brittle thin sheet. Trying to “cut” a thin sheet with a big object (with respect to the sheet’s thickness) results in a surprisingly regular wavy cut.
This wake is the results of coupling fracture propagation with large out-of-plane displacement of the sheet. The origin of this robust phenomenon lies in the geometry of possible buckling of the sheet.
Work in progress with B.Audoly (LMM) and P.M.Reis [ movies and more ] [ Nature science update ]
Here is a conference that i gave in 2016 (intended for fracture specialists) :