title: Enhanced protective role in materials with gradient structural orientations: Lessons from Nature.
abstract: Living organisms are adept at resisting contact deformation and damage by assembling protective surfaces with spatially varied mechanical properties, i.e., by creating functionally graded materials. Such gradients, together with multiple length-scale hierarchical structures, represent the two prime characteristics of many biological materials to be translated into engineering design. Here, we examine one design motif from a variety of biological tissues and materials where site-specific mechanical properties are generated for enhanced protection by adopting gradients in structural orientation over multiple length-scales, without manipulation of composition or microstructural dimension. Quantitative correlations are established between the structural orientations and local mechanical properties, such as stiffness, strength and fracture resistance; based on such gradients, the underlying mechanisms for the enhanced protective role of these materials are clarified. Theoretical analysis is presented and corroborated through numerical simulations of the indentation behavior of composites with distinct orientations. The design strategy of such bioinspired gradients is outlined in terms of the geometry of constituents. This study may offer a feasible approach towards generating functionally graded mechanical properties in synthetic materials for improved contact damage resistance.
  
  
  
  Living organisms are adept at resisting contact damage by assembling protective surfaces with spatially varied mechanical properties, i.e., by creating functionally-graded materials. Such gradients, together with multiple length-scale hierarchical structures, represent the prime characteristics of many biological materials. Here, we examine one design motif from a variety of biological tissues where site-specific mechanical properties are generated for enhanced protection by adopting gradients in structural orientation at multiple length-scales, without changes in composition or microstructural dimension. The design strategy of such bioinspired gradients is outlined in terms of the geometry of constituents. This study may offer a feasible approach towards generating functionally-graded mechanical properties in synthetic materials for improved damage resistance.
authors: Department of Materials Science and Engineering, University of California, Berkeley, CA 94720, USA; Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China.
authors: Zengqian
authors: Z
authors: Liu
authors: Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China.
authors: Yankun
authors: Y
authors: Zhu
authors: Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China.
authors: Da
authors: D
authors: Jiao
authors: Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China.
authors: Zhaoyong
authors: Z
authors: Weng
authors: Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China. Electronic address: zhfzhang@imr.ac.cn.
authors: Zhefeng
authors: Z
authors: Zhang
authors: Department of Materials Science and Engineering, University of California, Berkeley, CA 94720, USA. Electronic address: roritchie@lbl.gov.
authors: Robert O
authors: RO
authors: Ritchie
mesh_terms: D001672:Biocompatible Materials / Q000737:chemistry* / Q000494:pharmacology*; D032701:Biomimetics; D003198:Computer Simulation; D008422:Materials Testing / Q000379:methods*; D055595:Mechanical Phenomena
chemical_list: D001672:Biocompatible Materials
keywords: Bioinspired design; Biological materials; Functionally graded materials; Gradient; Structural orientation