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Fibre-Reinforced Composites with Nacre-Inspired Interphase

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Fibre-Reinforced Composites with Nacre-Inspired Interphase Fibre-Reinforced Composites with Nacre-Inspired Interphase: A Route Towards High Performance Toughened Hierarchical Composites by François De Luca A Thesis submitted in fulfilment of the requirements for the degree of Doctor of Philosophy and the Diploma of Imperial College London Chemical Engineering Department Imperial College London From June 2013 to December 2016 1 Abstract Conventional fibre-reinforced polymer composite materials are well known for their high strength, stiffness, low weight and chemical resistance but composites do fail catastrophically, in a brittle manner, with little prior warning. When a fibre breaks in tension, shear stresses transfer load previously carried by the broken fibre to neighbouring fibres through the matrix, leading to local stress concentrations. As tensile loading continues, fibre breaks accumulate in the composite, eventually leading to the formation of a critical cluster, which triggers the failure of the composite. The aim of this research was to develop a novel hierarchical composite architecture consisting of fibres decorated with a nanostructured coating embedded in a matrix. A high performance and tough nanostructured composite interphase, inspired by nacre, should provide additional toughness in tension. A Layer-by-Layer assembly method was used to assemble inorganic nanometre-wide platelets and a polyelectrolyte into a well-organised nanostructure, mimicking the “brick-and-mortar” architecture of nacre, which was developed and characterised. The nanostructure was successfully deposited around conventional reinforcing-fibres, such as carbon and glass fibres, and allowed for absorption of the energy arising from fibre breaks and substantial increase in debonding toughness in single fibre composite models. Impregnated fibre bundle composites were manufactured and tested in tension, which exhibited an increased tensile strength, strain to failure and work of fracture when the nanostructured composite interphase was incorporated. This work was part of the HiPerDuCT programme grant, collaboration between the departments of Aeronautics, Chemical Engineering, Chemistry and Mechanical Engineering of Imperial College London and the University of Bristol. 2 Declaration of Originality This manuscript is a description of the work achieved by the author in the Department of Chemical Engineering of Imperial College London between June 2013 to December 2016, under the supervision of Prof. Alexander Bismarck and Prof. Milo Shaffer. Except where acknowledged, the material presented is the original work of the author and no part of it has been submitted for a degree at Imperial College London or any other university. 3 Copyright Declaration The copyright of this thesis rests with the author and is made available under a Creative Commons Attribution Non-Commercial No Derivatives licence. Researchers are free to copy, distribute or transmit the thesis on the condition that they attribute it, that they do not use it for commercial purposes and that they do not alter, transform or build upon it. For any reuse or redistribution, researchers must make clear to others the licence terms of this work. 4 Acknowledgments First of all, my sincere gratitude goes to my supervisors, Prof. Milo Shaffer and Prof. Alexander Bismarck for entrusting a cutting-edge research PhD project to me and continuously providing me with guidance, inspiration and excellence. I am also grateful for their precious time they dedicated to follow my research, answer my concerns and transfer their true knowledge and passion. I would like to thank Jonny Blaker and Robert Menzel for their expertise and the successful transfer of the research project to me. They have been a great support during my first year to reach my independence and help me learn the skills required to pursuit a PhD. I am grateful to Joshua Elsdon for designing, building and maintaining the dipping robot throughout the entire research project. My keen appreciation goes to Adam Clancy for helping me modifying the surface of glass and carbon fibres and Noelia Rubio Carrero for characterising the surface of oxidised carbon fibres by XPS. I am indebted to Mahmoud Ardakani for the quality of his SEM training and regular help as well as his assistance on TEM and Cati Ware for her help on the preparation of a TEM sample using the FIB technique. Also, I would like to thank Sergio Sernicola for his availability and conducting in-situ SEM nanoindentation and Richard Sweeney for his assistance on XRD rocking curve acquisition. 5 I would like to thank my officemates, Konstanze Seidler, Hele Diao, Tomi Herceg, and Rosminah Shamsuddin for their support, availability, helpful discussion and consideration. A special thank goes to David Anthony for his in depth discussion, availability to assist me on composite testing and valuable help and advice. All my colleges from the PaCE and NanoHAC groups deserves sincere thanks for their support, friendliness and enthusiasm to share their experience and knowledge. So I would like to thank Henry Maples, Wonjun Lee, Stephen Hodge, Hin Chun Yau, Min Tang, Koon Yang, Hanna Leese, Edward White, Foivos Markoulidis, Mustafa Bayazit, Jonathan Weiner, Jonathan Davison, Cynthia Sheng Hu, Martina De Marco, Heather Au, Aaron Thong, Chris Roberts, Alice Leung, Eileen Brandley, and Sandy Fisher. I would like thank you, Eero Kontturi and Katri Kontturi, for your kindness and interesting discussions. Special thanks go to Gael Grail, Derrick Fam, Robert Woodward, Hugo De Luca and Marcel Lorenz for their friendship and time spent together outside work, which made my life and experience in London a real pleasure. Also, I am very grateful to my family and friends, who showed constant support throughout my PhD. Finally, I would like to thank the people from the Chemical Engineering department I had lunch with daily. Lastly, but not the least, I am very grateful to all the members of the HiPerDuCT programme grant team; Prof. Michael Wisnom, Prof. Paul Robinson, Prof. Kevin Potter, Soraia Pimenta, Gergely Czel, HaNa Yu, Jakub Rycerz, James Finley, James Serginson, James Trevarthen, Jingjing Sun, Joel Henry, Jonathan Fuller, Marco Longana, Meisam Jalalvand, Mohammad Fotouhi, Omar Bacarreza, Putu Suwarta, Stefano Del Rosso, Thomas Pozegic, Xun Wu, for all the discussions and advice during the whole PhD research project. I would also like to thank the UK Engineering and Physical Sciences Research Council (EPSRC) (grant EO/I02946X/1) and Alexander Bismarck’s F-account for funding. 6 Contents List of Publications/Patent ....................................................................................................... 12 List of Figures .......................................................................................................................... 14 List of Tables ........................................................................................................................... 25 List of Abbreviations ............................................................................................................... 26 1. Introduction .......................................................................................................................... 27 1.1 Motivation ...................................................................................................................... 27 1.2 Objectives ....................................................................................................................... 29 1.3 Approach ........................................................................................................................ 31 1.4 Structure of the thesis ..................................................................................................... 35 2. Literature Review................................................................................................................. 37 2.1 Fibre-reinforced polymer composites for load bearing applications ............................. 37 2.1.1 Fundamentals of fibre-reinforced composites ................................................... 37 2.1.2 Role of fibre-reinforced composite interfaces ................................................... 39 2.1.3 Catastrophic failure of fibre-reinforced composites .......................................... 40 2.2 Engineered fibre-reinforced composite interphases for energy absorption ................... 41 2.2.1 Energy absorbing fibre polymer coatings .......................................................... 42 2.2.2 Roughened interphases for interfacial mechanical frictions .............................. 44 2.2.3 Incorporation of nanofillers in interphase to toughen composites ..................... 45 2.2.4 Nanostructured interphases for toughened composite ....................................... 50 2.3 “Brick-and-mortar” structure of nacre ........................................................................... 53 2.3.1 Hierarchical structure of nacre ........................................................................... 53 2.3.2 Toughening mechanisms occurring in nacre ..................................................... 55 2.3.3 Tensile and shear responses of nacre ................................................................. 60 2.3.4 Scaling behaviour of nacre “brick-and-mortar” structure .................................. 62 2.3.5 Flaw tolerance of platelets ................................................................................. 64 2.4 Nacre-inspired structures...............................................................................................
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