title: Design of biomimetic fibrillar interfaces: 2. Mechanics of enhanced adhesion.
abstract: This study addresses the strength and toughness of generic fibrillar structures. We show that the stress sigmac required to pull a fibril out of adhesive contact with a substrate has the form sigma(c) = sigma(0)Phi(chi). In this equation, sigma(0) is the interfacial strength, Phi(chi) is a dimensionless function satisfying 0 <or= Phi(chi) <or= 1 and chi is a dimensionless parameter that depends on the interfacial properties, as well as the fibril stiffness and radius. Pull-off is flaw sensitive for chi >> 1, but is flaw insensitive for chi < 1. The important parameter chi also controls the stability of a homogeneously deformed non-fibrillar (flat) interface. Using these results, we show that the work to fail a unit area of fibrillar surface can be much higher than the intrinsic work of adhesion for a flat interface of the same material. In addition, we show that cross-sectional fibril dimensions control the pull-off force, which increases with decreasing fibril radius. Finally, an increase in fibril length is shown to increase the work necessary to separate a fibrillar interface. Besides our calculations involving a single fibril, we study the concept of equal load sharing (ELS) for a perfect interface containing many fibrils. We obtain the practical work of adhesion for an idealized fibrillated interface under equal load sharing. We then analyse the peeling of a fibrillar surface from a rigid substrate and establish a criterion for ELS.
authors.affiliation: Department of Theoretical and Applied Mechanics, Cornell University, 212 Kimball Hall, Ithaca, NY 14853, USA.
authors.forename: C-Y
authors.initials: CY
authors.lastname: Hui
authors.forename: N J
authors.initials: NJ
authors.lastname: Glassmaker
authors.forename: T
authors.initials: T
authors.lastname: Tang
authors.forename: A
authors.initials: A
authors.lastname: Jagota
mesh_terms: D000268:Adhesiveness; D001672:Biocompatible Materials / Q000737:chemistry*; D040761:Biomimetic Materials / Q000737:chemistry*; D019245:Compressive Strength; D003198:Computer Simulation; D004548:Elasticity; D024022:Fibrillar Collagens / Q000737:chemistry*; D008422:Materials Testing; D019563:Mechanics; D008956:Models, Chemical; D049329:Nanostructures / Q000737:chemistry* / Q000648:ultrastructure*; D013314:Stress, Mechanical; D013499:Surface Properties; D013718:Tensile Strength
chemical_list: D001672:Biocompatible Materials; D024022:Fibrillar Collagens