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Horns and Hooves a Dissertat UNIVERSITY OF CALIFORNIA SAN DIEGO Impact resistant and energy absorbent natural keratin materials: horns and hooves A dissertation submitted in partial satisfaction of the requirements for the degree of Doctor of Philosophy in Materials Science and Engineering by Wei Huang Committee in charge: Professor Joanna McKittrick, Chair Professor Shengqiang Cai Professor Yu Qiao Professor Jan Talbot Professor Michael Tolley 2018 Copyright Wei Huang, 2018 All rights reserved The Dissertation of Wei Huang is approved, and is acceptable in quality and form for publication on microfilm and electronically: ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ ____________________________________________________________ Chair University of California San Diego 2018 iii TABLE OF CONTENTS TABLE OF CONTENTS ............................................................................................................... iv LIST OF FIGURES ....................................................................................................................... ix LIST OF TABLES ....................................................................................................................... xxi ACKNOWLEDGEMENTS ........................................................................................................ xxii VITA .......................................................................................................................................... xxiv ABSTRACT OF DISSERTATION .......................................................................................... xxvii CHAPTER 1: INTRODUCTION ....................................................................................................1 1.1 Introduction to biological materials science......................................................................1 1.2 Impact resistance and energy absorption in biological materials ......................................3 1.2.1 Bone and antler ..........................................................................................................6 1.2.2 Nacre ........................................................................................................................12 1.2.3 Mantis shrimp dactyl club ........................................................................................14 1.3 Bioinspired designs .........................................................................................................16 1.3.1 Freeze casting...........................................................................................................16 1.3.2 Additive Manufacturing ...........................................................................................19 1.3.3 Bottom-up synthesis of nanocomposites .................................................................22 CHAPTER 2: BACKGROUND OF KERATIN ...........................................................................25 2.1 Natural keratin materials .................................................................................................25 2.2 Classification of keratin materials ...................................................................................26 2.2.1 Soft vs. hard .............................................................................................................26 2.2.2 Mineralized vs. non-mineralized .............................................................................27 iv 2.2.3 Offensive vs. defensive ............................................................................................28 2.3 Structure and properties of keratin ..................................................................................29 2.3.1 Multi-phase compositions ........................................................................................29 2.3.2 Multi-scale hierarchical structure ............................................................................31 2.3.3 Multi-mechanical properties ....................................................................................33 CHAPTER 3: STRUCTURE AND PROPERTIES OF BIGHORN SHEEP HORN ....................37 3.1 Introduction to bighorn sheep horn .................................................................................37 3.2 Experiments and methods ...............................................................................................40 3.2.1 High resolution X-ray micro-computed tomography (HR µ-CT) ...........................41 3.2.2 Optical and scanning electron microscopy imaging ................................................42 3.2.3 Transmission electron microscopy imaging ............................................................43 3.2.4 Compression tests ....................................................................................................43 3.2.5 Hopkinson bar impact recovery tests and failure surface imaging ..........................45 3.2.6 Statistical analysis ....................................................................................................46 3.3 Results and discussions ...................................................................................................46 3.3.1 Hierarchical structure of horn ..................................................................................46 3.3.2 Strain rate, anisotropy and water dependency of mechanical properties .................52 3.3.3 Hopkinson bar impact recovery test results and failure mechanisms ......................58 3.4 Conclusions .....................................................................................................................65 CHAPTER 4: STRUCTURE AND PROPERTIES OF DIFFERENT HORNS ...........................69 4.1 Introduction .....................................................................................................................69 4.2 Experiments and methods ...............................................................................................74 v 4.2.1 Materials preparation ...............................................................................................74 4.2.2 Structural characterization .......................................................................................74 4.2.3 Water absorption and FTIR .....................................................................................75 4.2.4 Compression and tensile tests ..................................................................................75 4.2.5 Impact tests ..............................................................................................................77 4.2.6 Statistical analysis ....................................................................................................78 4.3 Results and discussions ...................................................................................................78 4.3.1 Microstructures of the different horns .....................................................................78 4.3.2 Compression tests ....................................................................................................81 4.3.3 Tensile tests ..............................................................................................................88 4.3.4 Drop tower impact tests ...........................................................................................92 4.4 Conclusions .....................................................................................................................95 4.5 Supplementary information .............................................................................................97 CHAPTER 5: WATER EFFECTS ON HORN KERATIN .........................................................101 5.1 Introduction ...................................................................................................................101 5.2 Materials and methods ..................................................................................................102 5.2.1 Acquisition and preservation of horn samples .......................................................102 5.2.2 Synchrotron wide angle X-ray diffraction (WAXD) .............................................102 5.2.3 Fourier transform infrared spectroscopy (ATR-FTIR) ..........................................103 5.2.4 Tensile tests and fracture surface imaging .............................................................103 5.2.5 Viscoelastic behavior: Creep tests .........................................................................104 5.2.6 Compression recovery tests ...................................................................................105 vi 5.3 Results and discussions .................................................................................................106 5.3.1 Water effects on the structure of horn keratin .......................................................106 5.3.2 Water effects on tensile and creep properties ........................................................109 5.3.3 Water assisted recoverable behaviors ....................................................................113 5.4 Conclusions ...................................................................................................................117 5.5 Supplementary information ...........................................................................................119 CHAPTER
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