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A Self Healing Smart Syntactic Foam Based Grid Stiffened Sandwich Structure

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A Self Healing Smart Syntactic Foam Based Grid Stiffened Sandwich Structure Louisiana State University LSU Digital Commons LSU Doctoral Dissertations Graduate School 2009 A self healing smart syntactic foam based grid stiffened sandwich structure Manu Kuruvila John Louisiana State University and Agricultural and Mechanical College, [email protected] Follow this and additional works at: https://digitalcommons.lsu.edu/gradschool_dissertations Part of the Mechanical Engineering Commons Recommended Citation John, Manu Kuruvila, "A self healing smart syntactic foam based grid stiffened sandwich structure" (2009). LSU Doctoral Dissertations. 822. https://digitalcommons.lsu.edu/gradschool_dissertations/822 This Dissertation is brought to you for free and open access by the Graduate School at LSU Digital Commons. It has been accepted for inclusion in LSU Doctoral Dissertations by an authorized graduate school editor of LSU Digital Commons. For more information, please [email protected]. A SELF HEALING SMART SYNTACTIC FOAM BASED GRID STIFFENED SANDWICH STRUCTURE A Dissertation Submitted to the Graduate Faculty of Louisiana State University and Agricultural and Mechanical College in partial fulfillment of the requirements for the degree of Doctor of Philosophy in The Department of Mechanical Engineering by Manu Kuruvila John B.Tech, Mahatma Gandhi University, India, 2001. M.S., Tuskegee University, 2004. December 2009 ACKNOWLEDGEMENTS I would like to extend my heartfelt gratitude and thanks to Dr. Guoqiang Li, my major professor for his guidance and support provided during the course of this research work and the confidence he had in me. This work would not have been possible without his extensive help, valuable insight and time he invested in this research work. He has been my constant inspiration and mentor for both my course work and research work. I would also like to thank the support and guidance of my graduate committee, Dr. Dorel Moldovan, Dr. Su-Seng Pang, Dr. Muhammad Wahab, Dr. Steve Cai and Dr. Roberto Barbosa, who is acting as the Dean‘s representative. The help provided by Ms. Cindy Henk, Dr. Xiaogang Xie and Dr. Kun Lian in doing the TEM, SEM and DSC analysis is greatly appreciated. Also, the help from Dr. Phani Mylavarapu and my lab mates is greatly acknowledged. I wish to extend a very special thanks to my wife, Chindu Rajan for the constant moral support and motivation she has provided throughout my life and work. She has been a constant source of inspiration and energy for me. I also would like to express my gratitude to my parents Mr. John Kuruvilla and Mrs. Susan John for their encouragement in pursuing my dreams and their help in getting a better education. Their sacrifices and prayers are really appreciated. The technical advice and expertise regarding the ―polymerization‖ process, provided by my father Mr. John Kuruvilla, is highly appreciated at this point. I express my heartfelt gratitude to my younger brother, Dr. Jinu John and his wife Chinnu Simon for their love and moral support. I take this opportunity to thank my in-laws Mr. C.T. Rajan and Mrs. Gracy Rajan; sisters Anna Rajan and Sara Rajan. Extreme gratitude goes to Mr. Abraham George and family, Hari and Archana; Arun, Reshmi and their lovely kid Aishwarya; Dr. Deepu, Ammu and their lovely kid Daya; Dr. Felix ii and Suja; Fr. Boby Alex; Dr. Sundar, Mini and their handsome kid Vishnuh; Dr. Manoj and Sujitha; Gigi, Cherian, Prashanth, Jomish, Manjooran, Abhish and Ency, Ciby, Moncy, Reji, Surbhi, Aparna and Sitanshu. I would like to acknowledge the Economic Development Assistantship (EDA) for providing funding for this study, Louisiana Transportation and Research Center (LTRC) and NASA-EPSCoR as well. Finally, no words can express my gratitude to the author and finisher of my life, Lord and Savior Jesus Christ, for His grace, wisdom and guidance. iii TABLE OF CONTENTS ACKNOWLEDGEMENTS .................................................................................................... ii LIST OF TABLES ................................................................................................................ vi LIST OF FIGURES .............................................................................................................. vii ABSTRACT............................................................................................................................x CHAPTER 1. INTRODUCTION ............................................................................................1 1.1 Syntactic Foams ...........................................................................................................1 1.2 Syntactic Foam Cored Sandwiches ...............................................................................7 1.3 Grid Stiffened Syntactic Foam Cored Sandwiches ...................................................... 11 1.4 Limitations of Syntactic Foams and Foam Cored Sandwiches ..................................... 11 1.5 Self Healing Methods in Thermoset Polymer Systems ................................................ 12 1.5.1 Hollow Fiber Approach ...................................................................................... 13 1.5.2 Microencapsulation Approach ............................................................................ 14 1.5.3 Thermoplastic Additives .................................................................................... 15 1.5.4 Thermally Reversible Cross-linked Polymers ..................................................... 16 1.6 Shape Memory Polymers (SMP) ................................................................................. 18 1.7 Shape Memory Polymer Based Foams ........................................................................ 24 CHAPTER 2. SHAPE MEMORY POLYMER BASED SMART SYNTACTIC FOAM ....... 28 2.1 SMP Formulation ....................................................................................................... 29 2.1.1 Suggested Components and Curing Cycle .......................................................... 29 2.1.2 Polymerization Process ...................................................................................... 30 2.2 Materials ..................................................................................................................... 31 2.3 Smart Syntactic Foam Fabrication .............................................................................. 32 2.4 Transmission Electron Microscopy (TEM) ................................................................. 35 2.5 Differential Scanning Calorimetry (DSC) ................................................................... 36 2.6 Thermal Conductivity Measurements ......................................................................... 38 2.7 Uniaxial Flat-wise Compression Tests of Smart Foam ................................................ 40 CHAPTER 3. MICROMECHANICS MODELING OF MICROSTRUCTURE OF THE SMART FOAM .................................................................................................................... 43 3.1 Micromechanics Modeling ......................................................................................... 44 3.2 Model Formulation ..................................................................................................... 45 CHAPTER 4. SMART FOAM CORED SANDWICH .......................................................... 50 4.1 Materials .................................................................................................................... 51 4.2 Smart Foam Cored Sandwich Fabrication ................................................................... 51 4.3 Thermomechanical Programming ............................................................................... 53 4.4 Low Velocity Impact (LVI) Tests ............................................................................... 56 4.5 Compression After Impact (CAI) ................................................................................ 60 4.6 Ultrasonic and SEM Inspection................................................................................... 65 iv CHAPTER 5. GRID STIFFENED SMART SYNTACTIC FOAM CORED SANDWICH .... 69 5.1 Materials .................................................................................................................... 70 5.2 Grid Stiffened Smart Syntactic Foam Sandwich Fabrication ....................................... 70 5.3 Thermomechanical Programming ............................................................................... 72 5.4 Low Velocity Impact (LVI) Tests and Self-Healing .................................................... 73 5.4.1 Low Energy Impact (30 J) .................................................................................. 74 5.4.2 High Energy Impact (53 J) ................................................................................. 79 5.5 Wave Propagation during Impact in Grid Stiffened Sandwich ..................................... 82 5.6 Compression After Impact (CAI) ................................................................................ 83 5.6.1 Low Energy Impact (30 J) .................................................................................. 84 5.6.2 High Energy Impact (53 J) ................................................................................. 89 5.7 Non-Destructive Ultrasonic C-scan Inspection ............................................................ 92 5.8 Visual Inspection ........................................................................................................ 95 CHAPTER 6. CONCLUSIONS AND
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