| Summary: | Composites are becoming increasingly popular in the world of manufacturing due to its lightweight yet impressive physical properties. They are especially prevalent in industries where weight plays a major role, covering a wide range of industries from aerospace to sports. With the increased emphasis on development in composites technology, the potential for development also provides a promising avenue in research.
Ice hockey sticks have continually evolved with the times, from being predominantly wooden to aluminium and now carbon fibre composites. These hockey sticks are generally manufactured using prepreg methods, where the resin has already been impregnated into the fibre reinforcements prior to manufacturing. However, the prepreg process is a highly arduous process which requires highly skilled labour and is limited in terms of its automation potential. Thus, an alternative method of manufacturing called bladder assisted resin transfer moulding (BRTM) which is also able to manufacture hollow composite parts is to be proposed in this project due to its relative lower cost and its higher room for automation.
The resin that is generally used for these hockey sticks are thermoset epoxy resins, which have a lower curing temperature as well as impressive mechanical properties. Thermoplastic resins, on the other hand, have a higher curing temperature, which adds to the complexity and cost of manufacturing. However, thermoplastic resins have superior resistance to damage as well as impact absorption, together with being less brittle. The development of a new thermoplastic resin, Elium® cures at room temperature. This therefore provides an attractive proposition of developing a composite with the superior properties of thermoplastic parts, whilst having a lower processing temperature.
Thermoplastic fibres provide good toughness and ductility, low cost but have low stiffness. To improve the stiffness of shafts, hybrid carbon-thermoplastic fibres were manufactured to combine the qualities of carbon such as stiffness and specific strength, with thermoplastic fibres such as its toughness and ductility. Additionally, hybrid carbon-thermoplastic fibres could provide a cost-effective alternative relative to carbon fibre due to the lower carbon content, whilst not compromising entirely on the benefits of carbon fibre.
This project therefore entails the manufacturing and characterisation of thermoplastic hollow composite shafts for ice hockey sticks. While there are plenty of hockey sticks made of prepreg carbon/epoxy composites, there are limited studies on that of thermoplastic fibres and resins. This project will thus manufacture these thermoplastic composite parts using BRTM and analyse these fibres bonding with Elium® and epoxy resins. The parts will then be put under low velocity impact (LVI) as well as three-point bending flexural tests to develop suitable alternatives to the carbon/epoxy prepreg composites currently in the market.
The results from the mechanical tests displayed promising results for hybrid carbon-thermoplastic composites, relative to pure thermoplastic composites. There were significant improvements in the strength and stiffness of the hybrid composites, with hybrid composites achieving about 13-30% higher peak load relative to the pure thermoplastic composites, coupled with 90-200% improved bending stiffness. A similar trend was also observed for Elium® thermoplastic composites relative to epoxy thermoset resins, with improvements ranging from 6-32% higher peak load performance and 6-25% higher bending stiffness.
The initial results from this final year project paves a new way to use hybrid thermoplastic composite shafts as deliberated on their manufacturing and the mechanical performances.
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