THE UNIVERSITY OF BIRMINGHAM Department of Metallurgy and Materials Stiffness variation in hockey sticks and the impact on stick performance Graeme Nigel Carlisle 788002 Submitted for the degree of Masters of Research – Science and Engineering of Materials August 2011 Department of Metallurgy and Materials 1 University of Birmingham Research Archive e-theses repository This unpublished thesis/dissertation is copyright of the author and/or third parties. The intellectual property rights of the author or third parties in respect of this work are as defined by The Copyright Designs and Patents Act 1988 or as modified by any successor legislation. Any use made of information contained in this thesis/dissertation must be in accordance with that legislation and must be properly acknowledged. Further distribution or reproduction in any format is prohibited without the permission of the copyright holder. Stiffness variation in hockey sticks and the impact on stick performance Graeme Nigel Carlisle Submitted with corrections for the degree of Masters of Research – Science and Engineering of Materials August 2011 Multiple sectioned shafts of carbon fibre composite were modelled using Composite Design Analysis software in order to replicate the range of flexural rigidities shown across the current field hockey stick market. The shafts were then manufactured using hand lay-up and hot-pressing techniques, tested under static and dynamic conditions and the goodness of their relationship with the modelled behaviour was assessed. The shafts were also analysed microscopically for volume fraction, ply-orientation and the interaction between the varied lay-up sections. The modelling gave a good understanding of the trend of behaviour that was to be expected, but was not accurate enough to predict experimental values. It is possible to create multiple sectioned CFRP shafts that can be controlled for overall flexural rigidity and also strain distribution or “kick-point”. The hand lay-up and hot pressing technique produces consistent volume fraction and accurate fibre orientation, however the seams at which the sections join requires further investigation and development. The relationship between stick stiffness and ball speed validated previous research, stiffer shafts produced a higher CoR in the drop ball test. There is scope to introduce this stiffness control of the bending behaviour into hockey sticks, by either material properties or section moment of area. Keywords: CFRP, Field Hockey, CoDA Modelling, Composite Manufacture Techniques. 2 Contents Abstract 2 Nomenclature 5 1 Introduction ................................................................................................................................... 6 1.1 History of the game ............................................................................................................................ 6 1.2 Equipment function and FIH rules ............................................................................................... 9 1.2.1 The stick ............................................................................................................................................................ 9 1.2.2 The ball ............................................................................................................................................................ 11 1.3 Composite materials ...................................................................................................................... 12 1.3.1 Polymer matrix composites .................................................................................................................... 12 1.3.2 Modulus of unidirectional composites and laminates ................................................................. 12 1.4 Modification of stiffness ................................................................................................................ 14 1.5 Aims and Objectives ....................................................................................................................... 19 2 Modelling of shaft behaviour ................................................................................................. 20 2.1 Introduction ...................................................................................................................................... 20 2.2 Methodology ...................................................................................................................................... 20 2.3 Results and discussion................................................................................................................... 24 3 Preliminary Panel analysis ..................................................................................................... 26 3.1 Methodology ...................................................................................................................................... 26 3.1.1 Quasi-static flexure ..................................................................................................................................... 26 3.1.2 Optical analysis ............................................................................................................................................ 27 3.2 Results and Discussion .................................................................................................................. 28 3.2.1 Quasi-static flexure ..................................................................................................................................... 28 3.2.2 Optical analysis ............................................................................................................................................ 28 4 Control shafts ............................................................................................................................... 32 4.1 Methodology ...................................................................................................................................... 32 4.1.1 Manufacture .................................................................................................................................................. 33 4.1.2 Dimensions .................................................................................................................................................... 33 4.1.3 Optical analysis ............................................................................................................................................ 34 4.1.4 Quasi-static shaft flexure.......................................................................................................................... 34 4.2 Results and Discussion .................................................................................................................. 35 4.2.1 Dimensions .................................................................................................................................................... 35 4.2.2 Optical analysis ............................................................................................................................................ 36 4.2.3 Quasi-static shaft flexure.......................................................................................................................... 37 5 Multiple section shafts .............................................................................................................. 38 5.1 Methodology ...................................................................................................................................... 38 5.1.1 Manufacture .................................................................................................................................................. 38 5.1.2 Hot pressing .................................................................................................................................................. 39 5.1.3 Dimensions .................................................................................................................................................... 40 5.1.4 Quasi-static shaft flexure.......................................................................................................................... 41 5.1.5 Dynamic drop-ball shaft flexure............................................................................................................ 42 5.1.6 Strain distribution ....................................................................................................................................... 44 5.1.7 Optical analysis ............................................................................................................................................ 45 5.2 Results and Discussion .................................................................................................................. 46 3 5.2.1 Dimensions .................................................................................................................................................... 46 5.2.2 Quasi-static shaft flexure.......................................................................................................................... 48 5.2.3 Dynamic drop-ball shaft flexure............................................................................................................ 54 5.2.4 Strain distribution ......................................................................................................................................