title: Mechanics of fragmentation of crocodile skin and other thin films.
abstract: Fragmentation of thin layers of materials is mediated by a network of cracks on its surface. It is commonly seen in dehydrated paintings or asphalt pavements and even in graphene or other two-dimensional materials, but is also observed in the characteristic polygonal pattern on a crocodile's head. Here, we build a simple mechanical model of a thin film and investigate the generation and development of fragmentation patterns as the material is exposed to various modes of deformation. We find that the characteristic size of fragmentation, defined by the mean diameter of polygons, is strictly governed by mechanical properties of the film material. Our result demonstrates that skin fragmentation on the head of crocodiles is dominated by that it features a small ratio between the fracture energy and Young's modulus, and the patterns agree well with experimental observations. Understanding this mechanics-driven process could be applied to improve the lifetime and reliability of thin film coatings by mimicking crocodile skin.
authors.affiliation: 1] Laboratory for Atomistic and Molecular Mechanics (LAMM), Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, 77 Massachusetts Ave., Room 1-239, Cambridge 02139, MA, USA [2] Center for Computational Engineering, Massachusetts Institute of Technology, 77 Massachusetts Ave., Cambridge, MA 02139, USA.
authors.forename: Zhao
authors.initials: Z
authors.lastname: Qin
authors.affiliation: 1] Laboratory of Bio-Inspired & Graphene Nanomechanics, Department of Civil, Environmental and Mechanical Engineering, Università di Trento, via Mesiano, 77 I-38123 Trento, Italy [2] Center for Materials and Microsystems, Fondazione Bruno Kessler, Via Sommarive 18, 38123 Povo (Trento) [3] School of Engineering & Materials Science, Queen Mary University of London, Mile End Road, London E1 4NS, UK.
authors.forename: Nicola M
authors.initials: NM
authors.lastname: Pugno
authors.affiliation: 1] Laboratory for Atomistic and Molecular Mechanics (LAMM), Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, 77 Massachusetts Ave., Room 1-239, Cambridge 02139, MA, USA [2] Center for Computational Engineering, Massachusetts Institute of Technology, 77 Massachusetts Ave., Cambridge, MA 02139, USA [3] Center for Materials Science and Engineering, Massachusetts Institute of Technology, 77 Massachusetts Ave., Cambridge, MA 02139, USA.
authors.forename: Markus J
authors.initials: MJ
authors.lastname: Buehler
mesh_terms: D000489:Alligators and Crocodiles; D000818:Animals; D008422:Materials Testing; D008962:Models, Theoretical; D012867:Skin / Q000737:chemistry*; D012879:Skin Physiological Phenomena; D013499:Surface Properties