title: Forbidden directions for the fracture of thin anisotropic sheets: an analogy with the Wulff plot.
abstract: It is often postulated that quasistatic cracks propagate along the direction allowing fracture for the lowest load. Nevertheless, this statement is debated, in particular for anisotropic materials. We performed tearing experiments in anisotropic brittle thin sheets that validate this principle in the case of weak anisotropy. We also predict the existence of forbidden directions and facets in strongly anisotropic materials, through an analogy with the description of equilibrium shapes in crystals. However, we observe cracks that do not necessarily follow the easiest direction but can select a harder direction, which is only locally more advantageous than neighboring paths. These results challenge the traditional description of fracture propagation, and we suggest a modified, less restrictive criterion compatible with our experimental observations.
authors.affiliation: PMMH, UMR 7636 ESPCI/CNRS/UPMC/U.Diderot, 10 rue Vauquelin, 75231 Paris CEDEX 05, France.
authors.forename: Atsushi
authors.initials: A
authors.lastname: Takei
authors.affiliation: PMMH, UMR 7636 ESPCI/CNRS/UPMC/U.Diderot, 10 rue Vauquelin, 75231 Paris CEDEX 05, France.
authors.forename: Benoît
authors.initials: B
authors.lastname: Roman
authors.affiliation: PMMH, UMR 7636 ESPCI/CNRS/UPMC/U.Diderot, 10 rue Vauquelin, 75231 Paris CEDEX 05, France.
authors.forename: José
authors.initials: J
authors.lastname: Bico
authors.affiliation: Departamento de Física, Universidad de Santiago de Chile, Avenida Ecuador 3493, 9170124 Estación Central, Santiago, Chile.
authors.forename: Eugenio
authors.initials: E
authors.lastname: Hamm
authors.affiliation: Departamento de Física, Universidad de Santiago de Chile, Avenida Ecuador 3493, 9170124 Estación Central, Santiago, Chile.
authors.forename: Francisco
authors.initials: F
authors.lastname: Melo
mesh_terms: D016880:Anisotropy; D055595:Mechanical Phenomena; D008962:Models, Theoretical; D013314:Stress, Mechanical; D013816:Thermodynamics