Material and Construction Influences on Football Impact Behaviour by Henry Hanson A doctoral thesis submitted in partial fulfilment of the requirements for the award of Doctor of Philosophy of Loughborough University November 2014 © by Henry Hanson 2014 0 Acknowledgements To my friends and family for supporting my decision to move abroad and encouragement throughout, my fellow researchers for creating a fun and intellectually stimulating environment, my advisors Andy Harland, Dan Price, Chris Holmes and Tim Lucas for their perspective and expertise Katherine Boden, Steve Carr, Max Farrand, and Andrew Hallam for making the office and labs efficient and productive places to work. Thank you! Contents Abstract ................................................................................................................................................... 5 1 Introduction .................................................................................................................................... 1 1.1 Development of Game ............................................................................................................ 1 1.2 Football Development and Requirements .............................................................................. 3 1.2.1 Football Regulations ....................................................................................................... 4 1.2.2 Football Loading Conditions............................................................................................ 5 1.2.3 Current Constructions, Materials, and Manufacturing Methods ................................... 5 1.2.4 Recent developments ..................................................................................................... 8 1.3 Research Aims and Objectives ................................................................................................ 8 2 Literature Review .......................................................................................................................... 10 2.1 Football Impact Behaviour .................................................................................................... 10 2.1.1 Coefficient of Restitution .............................................................................................. 11 2.1.2 Contact Time and Contact Force ................................................................................... 12 2.1.3 Deformation .................................................................................................................. 14 2.2 Materials ............................................................................................................................... 15 2.2.1 Material Properties of Interest ..................................................................................... 15 2.2.2 Material Characterisation for FEA ................................................................................. 17 2.2.3 Material Testing for FEA ................................................................................................ 17 2.3 Football Simulation ............................................................................................................... 20 2.3.1 Aerodynamics ............................................................................................................... 20 2.3.2 Structural Simulation .................................................................................................... 21 2.3.3 D.O.E. ............................................................................................................................ 23 2.4 Ball Impact Acoustics ............................................................................................................ 24 2.5 Summary ............................................................................................................................... 26 3 Materials Characterisation for Footballs ...................................................................................... 28 3.1 Intentions .............................................................................................................................. 28 3.2 Basic Test Protocol ................................................................................................................ 28 3.3 Variations in Test Protocol .................................................................................................... 32 3.3.1 Representative Strain Rate vs. Representative Strain Magnitude ................................ 32 3.3.2 Fabric Characterisation ................................................................................................. 35 3.3.3 Materials Before and After Processing ......................................................................... 41 3.3.4 Testing Composite Sections .......................................................................................... 45 3.4 Temperature-Dependency .................................................................................................... 47 3.5 Summary ............................................................................................................................... 49 4 Finite Element Analysis Models .................................................................................................... 51 4.1 Intentions .............................................................................................................................. 51 4.2 Basic Model ........................................................................................................................... 51 4.2.1 Mesh Refinement .......................................................................................................... 53 4.3 Desired Outputs .................................................................................................................... 56 4.4 Surface Deformation Modelling ............................................................................................ 57 4.5 Simulating Spatial Variation of Internal Pressure ................................................................. 59 4.6 Parametric Model Creation ................................................................................................... 65 4.7 Boundary Conditions ............................................................................................................. 66 4.8 Validation .............................................................................................................................. 67 4.9 Summary ............................................................................................................................... 70 5 Impact Behaviour .......................................................................................................................... 71 5.1 Intentions .............................................................................................................................. 71 5.2 Validation .............................................................................................................................. 71 5.2.1 High-Speed Impact Validation Lab Methods ................................................................ 72 5.2.2 High-Speed Video Processing Methods ........................................................................ 74 5.2.3 High-Speed Impact Validation Challenges .................................................................... 75 5.2.4 Drop Test Validation Methods ...................................................................................... 75 5.2.5 Deformation at 0° and 45° Impact Orientations ........................................................... 77 5.3 Patch Carcass Deformation and Rebound Deviation ............................................................ 79 5.4 Impact Size vs. Anisotropic Element Size .............................................................................. 82 5.5 Outer Panel Local Deformation ............................................................................................ 88 5.6 Patch Carcass Case Studies ................................................................................................... 91 5.6.1 Modified Patch Carcass ................................................................................................. 91 5.6.2 Novel Carcass Concepts ................................................................................................ 96 5.6.3 Picasso ......................................................................................................................... 102 5.6.4 Tucasa ......................................................................................................................... 104 5.6.5 Triakis .......................................................................................................................... 105 5.7 Partial Net Carcass Prototype Comparisons ....................................................................... 106 5.8 Summary ............................................................................................................................. 109 6 Design of Experiments and Optimisation ................................................................................... 110 6.1 Intentions ............................................................................................................................ 110 6.2 Simple Yarn Orientation Study ...........................................................................................