Star shaped crack pattern of broken windows

Nicolas Vandenberghe (1) , Romain Vermorel (1) , Emmanuel Villermaux (1)

1 IRPHE - Institut de Recherche sur les Phénomènes Hors Equilibre

Broken thin brittle plates like windows and windshields are ubiquitous in our environment. When impacted locally, they typically present a pattern of cracks extending radially outwards from the impact point. We study the variation of the pattern of cracks by performing controlled transverse impacts on brittle plates over a broad range of impact speed, plate thickness and material properties, and we establish from experiments a global scaling law for the number of radial cracks incorporating all these parameters. A model based on Griffith's theory of fracture combining plate bending elastic energy and fracture energy accounts for our observations. These findings indicate how the post-mortem shape of broken samples are related to material properties and impact parameters, a procedure relevant to forensic science, archaeology or astrophysics.

Mots clés: radial cracks; brittle fracture; fragmentation; impacts; fracture energy; forensics; plates

Domaines: Mécanique des solides [physics.class-ph]; Mécanique des solides [physics.class-ph]; Mécanique des matériaux [physics.class-ph]; Mécanique des matériaux [physics.class-ph]; Physique Classique [physics.class-ph]; Physique mathématique [math-ph]; Physique mathématique [math-ph]; Matériaux et structures en mécanique [physics.class-ph]; Matériaux et structures en mécanique [physics.class-ph]; Physique Générale [physics.gen-ph]

Nicolas Vandenberghe, Romain Vermorel, Emmanuel Villermaux. Star shaped crack pattern of broken windows. Physical Review Letters, 2013, 110 (17), pp.174302. ⟨10.1103/PhysRevLett.110.174302⟩. ⟨hal-00857239⟩