The Integration of Nickel-Titanium Shape
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DYNAMIC CONTROL OF ACTIVE TEXTILES: THE INTEGRATION OF NICKEL- TITANIUM SHAPE MEMORY ALLOYS AND THE MANIPULATION OF WOVEN STRUCTURES Patrick E. Dyer A thesis submitted in partial fulfilment of the requirements of the University of Brighton for the degree of Doctor of Philosophy January 2010 The University of Brighton Abstract The integration of wire-form, nickel titanium (NiTi), shape memory alloys (SMA), within woven structures, offers the potential to generate unique properties in this bi-material composite. The combination of two materials, one of which can be modified with regard to its stiffness and elastic behaviour, gives further latitude for the textile designer to adapt a combination of functional and aesthetic properties in constructed textiles. To date, there has been limited research into the impact textile structures could have on both direct and indirect shape transfer from an integrated SMA component. This thesis overviews the integration of shape memory materials in textile structures informed through practice. In combination with a variety of natural and synthetic yarns, the investigation has examined how the manipulation of simple woven structures can be used to alter the direct and indirect mechanical shape transfer characteristics of from integrated NiTi components. In particular this thesis examines the influence of cloth sett, woven structure, and choice of yarn in combination with a variety of NiTi wire and ribbon. Composite samples were woven and the mechanical relationship with the integrated NiTi was investigated through a series of bend and tensile tests using mechanical mass loading and resultant extraction. The samples were validated by computer controlled tensile / compression testing machines. Subjective evaluations of visual and tactile properties were also conducted, together with comparative topography and morphology investigations using scanning electron microscopy. The results of this research have been catalogued forming an extensive technical database, searchable by single or multiple design variables. This database is a valuable resource that will support future decision making within this emerging design field. 2 Contents Abstract............................................................................................................................................ 2 Contents.......................................................................................................................................... 3 List of figures................................................................................................................................... 7 List of tables ....................................................................................................................................10 List of equations...............................................................................................................................11 Definitions........................................................................................................................................12 Abbreviations...................................................................................................................................13 Declaration.......................................................................................................................................14 Acknowledgement............................................................................................................................16 1 Introduction ................................................................................................... 17 1.1 Background to this research ......................................................................................... 17 1.2 Research questions ........................................................................................................ 18 1.3 Justification for research ............................................................................................... 18 1.4 Methodology .................................................................................................................... 20 1.5 Outline of thesis .............................................................................................................. 21 1.6 Delimitations of the research ......................................................................................... 24 2 Literature review ........................................................................................... 25 2.1 Material science and materials engineering ................................................................. 25 2.1.1 The Biomimetic approach to material science .............................................................. 25 2.1.2 Textiles: flexible materials ............................................................................................. 27 2.1.2.1 Characteristics and development of woven textiles .............................................. 27 2.1.2.2 Development of the textiles design and science interface .................................... 28 2.2 Shape memory materials (SMM) .................................................................................... 29 2.2.1 Shape memory materials (SMM) suitable for textile applications ................................. 29 2.2.2 Shape Memory Polymers .............................................................................................. 31 2.2.2.1 Elastic shape memory polymers ........................................................................... 32 2.2.2.2 Thermal shape memory polymers ......................................................................... 32 2.2.2.3 Micro scale thermal shape memory polymers ...................................................... 32 2.2.2.4 Macro scale thermal shape memory polymers ..................................................... 33 2.2.3 Shape memory alloys .................................................................................................... 34 2.2.3.1 Magnetic shape memory alloys ............................................................................. 35 2.2.3.2 Comparison between NiTi and Cu based alloys ................................................... 35 2.2.4 Summary of shape memory materials suitable for active textiles ................................. 37 2.3 Nickel Titanium shape memory alloy ............................................................................ 37 2.3.1 History ........................................................................................................................... 37 2.3.2 Development of NiTi ...................................................................................................... 38 2.3.3 Thermoelastic Martensitic transformation of NiTi .......................................................... 39 2.3.4 Hysteresis ...................................................................................................................... 40 2.3.5 Thermal shape memory ................................................................................................ 41 2.3.5.1 One way thermal shape memory .......................................................................... 41 3 2.3.5.2 Two way thermal shape memory .......................................................................... 42 2.3.6 Superelastic shape memory .......................................................................................... 42 2.3.7 Mechanical properties of NiTi ........................................................................................ 43 2.3.8 Fabrication and forming ................................................................................................ 44 2.3.9 Biocompatibility ............................................................................................................. 45 2.3.10 Shape setting SMA components ................................................................................... 45 2.3.10.1 Conventional shape setting in an oven ................................................................. 46 2.3.10.2 Underwater and low temperature shape training .................................................. 46 2.4 NiTi SMA mechanisms and applications ...................................................................... 46 2.4.1 Passive applications ...................................................................................................... 47 2.4.2 Active applications......................................................................................................... 48 2.4.3 Actuator types ............................................................................................................... 49 2.4.3.1 Mass and SMA wire actuator ................................................................................ 49 2.4.3.2 Spring and SMA wire actuator .............................................................................. 49 2.4.3.3 SMA and SMA wire actuator ................................................................................. 50 2.4.4 Electrical control ............................................................................................................ 50 2.5 Active NiTi composites ................................................................................................... 51 2.5.1 Vibration and stiffness control ....................................................................................... 52 2.5.2 Active shape control .....................................................................................................