Mechanical and Optical Characterization of the Hercules Beetle Elytra
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Calhoun: The NPS Institutional Archive Theses and Dissertations Thesis Collection 2014-09 Bioinspired composites design: mechanical and optical characterization of the Hercules beetle elytra Bickings, Conrad M. Monterey, California: Naval Postgraduate School http://hdl.handle.net/10945/48128 NAVAL POSTGRADUATE SCHOOL MONTEREY, CALIFORNIA THESIS BIOINSPIRED COMPOSITES DESIGN: MECHANICAL AND OPTICAL CHARACTERIZATION OF THE HERCULES BEETLE ELYTRA by Conrad M. Bickings September 2014 Thesis Advisor: Claudia C. Luhrs Co-Advisor: Nancy M. Haegel Approved for public release; distribution is unlimited THIS PAGE INTENTIONALLY LEFT BLANK REPORT DOCUMENTATION PAGE Form Approved OMB No. 0704-0188 Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instruction, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, to Washington headquarters Services, Directorate for Information Operations and Reports, 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302, and to the Office of Management and Budget, Paperwork Reduction Project (0704-0188) Washington DC 20503. 1. AGENCY USE ONLY (Leave blank) 2. REPORT DATE 3. REPORT TYPE AND DATES COVERED September 2014 Master’s Thesis 4. TITLE AND SUBTITLE 5. FUNDING NUMBERS BIOINSPIRED COMPOSITES DESIGN: MECHANICAL AND OPTICAL CHARACTERIZATION OF THE HERCULES BEETLE ELYTRA 6. AUTHOR(S) CONRAD M. BICKINGS 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) 8. PERFORMING ORGANIZATION Naval Postgraduate School REPORT NUMBER Monterey, CA 93943-5000 9. SPONSORING /MONITORING AGENCY NAME(S) AND ADDRESS(ES) 10. SPONSORING/MONITORING N/A AGENCY REPORT NUMBER 11. SUPPLEMENTARY NOTES The views expressed in this thesis are those of the author and do not reflect the official policy or position of the Department of Defense or the U.S. Government. IRB Protocol number ____N/A____. 12a. DISTRIBUTION / AVAILABILITY STATEMENT 12b. DISTRIBUTION CODE Approved for public release; distribution is unlimited 13. ABSTRACT (maximum 200 words) Reproducing the structure of biological materials has rendered synthetic materials with remarkable properties. Here we studied the features of a rhinoceros beetle, Dynastes Hercules, aiming to understand its structural components and relate them to its properties. This beetle changes color, from yellow-green to completely black in diverse humidity conditions due to a porous layer that absorbs water. The objectives of the work included the characterization of the reflectance spectra of the porous layer in the visible and shortwave infrared regions, and, for the first time, determine its mechanical properties. This work provides the foundation for a longer-term objective: design and generate synthetic materials that mimic the functionality of biological materials. In this particular case, the new multifunctional material could find application as lightweight camouflage effective under visible and shortwave infrared conditions. Elytra samples taken from dead specimens of Dynastes Hercules were sectioned and prepared for optical property characterization and mechanical testing. Spectral reflectance measurements were taken under wet and dry conditions which showed a similar signature to foliage. Optical and Scanning Electron Microscopy along with Focus Ion Beam cross-sectional analysis were used to examine the pores and tubular structures that allow water into the sponge-like layer that promotes the color changes. Tensile tests were used to determine Young’s Modulus and tensile strength of the elytra. Hardness and density measurements are also included. The measurements rendered specific modulus and specific strength values similar to wood. In addition, attempts to mimic the porous layer using anodizing techniques to render tubular inorganic structures are reported. 14. SUBJECT TERMS Bioinspired materials, Shortwave Infrared, SWIR, Biomimetics, Camouflage, 15. NUMBER OF Anodizing Titanium PAGES 95 16. PRICE CODE 17. SECURITY 18. SECURITY 19. SECURITY 20. LIMITATION OF CLASSIFICATION OF CLASSIFICATION OF THIS CLASSIFICATION OF ABSTRACT REPORT PAGE ABSTRACT Unclassified Unclassified Unclassified UU NSN 7540-01-280-5500 Standard Form 298 (Rev. 2-89) Prescribed by ANSI Std. 239-18 i THIS PAGE INTENTIONALLY LEFT BLANK ii Approved for public release; distribution is unlimited BIOINSPIRED COMPOSITES DESIGN: MECHANICAL AND OPTICAL CHARACTERIZATION OF THE HERCULES BEETLE ELYTRA Conrad M. Bickings Lieutenant, United States Navy B.S., United States Naval Academy, 2009 Submitted in partial fulfillment of the requirements for the degree of MECHANICAL ENGINEER AND MASTER OF SCIENCE IN MECHANICAL ENGINEERING from the NAVAL POSTGRADUATE SCHOOL September 2014 Author: Conrad M. Bickings Approved by: Claudia C. Luhrs Thesis Advisor Nancy M. Haegel Co-Advisor Garth V. Hobson Chair, Department of Mechanical and Aerospace Engineering iii THIS PAGE INTENTIONALLY LEFT BLANK iv ABSTRACT Reproducing the structure of biological materials has rendered synthetic materials with remarkable properties. Here, we studied the features of a rhinoceros beetle, Dynastes Hercules, aiming to understand its structural components and relate them to its properties. This beetle changes color from yellow-green to completely black in diverse humidity conditions due to a porous layer that absorbs water. The objectives of this work included the characterization of the reflectance spectra of the porous layer in the visible and shortwave infrared regions, and, for the first time, determining its mechanical properties. This work provides the foundation for a longer-term objective: design and generate synthetic materials that mimic the functionality of biological materials. In this particular case, the new multifunctional material could find application as lightweight camouflage effective under visible and shortwave infrared conditions. Elytra samples taken from dead specimens of Dynastes Hercules were sectioned and prepared for optical property characterization and mechanical testing. Spectral reflectance measurements were taken under wet and dry conditions, which showed a similar signature to foliage. Optical and Scanning Electron Microscopy along with focus ion beam cross-sectional analysis were used to examine the pores and tubular structures that allow water into the sponge-like layer that promotes the color changes. Tensile tests were used to determine Young’s Modulus and tensile strength of the elytra. Hardness and density measurements are also included. The measurements rendered specific modulus and specific strength values similar to wood. In addition, attempts to mimic the porous layer using anodizing techniques to render tubular inorganic structures are reported. v THIS PAGE INTENTIONALLY LEFT BLANK vi TABLE OF CONTENTS I. INTRODUCTION........................................................................................................1 A. OVERVIEW .....................................................................................................1 B. BIOINSPIRED MATERIALS ........................................................................2 C. THESIS OBJECTIVES ...................................................................................5 D. HYPOTHESIS..................................................................................................6 E. NAVAL RELEVANCE OF THE TOPIC .....................................................6 F. THESIS OUTLINE ..........................................................................................7 II. EXPERIMENTAL METHODS .................................................................................9 A. BEETLE ANATOMY .....................................................................................9 1. Dissection of the Beetle ......................................................................10 B. HUMIDITY AND COLOR CHANGE ........................................................11 1. Set-Up ..................................................................................................11 2. Procedure ............................................................................................12 C. MICROSTRUCTURAL ................................................................................13 1. OPTICAL MICROSCOPY...............................................................13 a. Set-Up ......................................................................................14 b. Procedure ................................................................................15 2. Scanning Electron Microscopy .........................................................15 a. Set-Up ......................................................................................16 b. Procedure ................................................................................17 D. OPTICAL CHARACTERIZATION ...........................................................17 1. Set-Up ..................................................................................................18 2. Procedure ............................................................................................21 E. DENSITY ........................................................................................................22 1. Set-Up and Procedure........................................................................23