COMPOSITES
COMPOSITES
THE CORRECT COMPOSITE
Carbon fi bre or fi breglass? Kim Sjödahl advises how to pick the best composite for your application
Y
ou wouldn’t attempt to delicately manicure a bonsai tree with a chainsaw, even if it would be entertaining to watch. T is may
seem obvious, but there are many fi elds where selecting the right tool is a vital ingredient to success. In the composites industry, customers often request carbon fi bre when in fact fi breglass is a better suited high-performance material for their needs. Carbon fi bre is often hailed as the material of the future. When people think of carbon fi bre, they’re likely to envision slick sports cars with doors that open vertically or, if they are industry focused, wind turbine blades longer than previously imaginable. For most composite producers, carbon fi bre is the material that gets customers and their design engineers interested in composites – before they realise that other composites such as fi breglass are better suited to their project. Sports cars, road bikes and professional tennis rackets are all extensively made using carbon fi bre. T is is because these applications require a low density and high ultimate tensile strength material to maximise weight advantages. However, this doesn’t mean that carbon fi bre is perfect for every application.
RAISING THE GLASS In many cases when clients are looking for carbon fi bre, the material that better suits their needs is fi breglass. In fact, it could be said that fi breglass was the fi rst ever high- performance material, with its conception dating back to before the Second World
War. Fibreglass has proven its usefulness over and over, from use in door or window frame profi les to telescoping poles, in automotive applications to rail joints and telecommunications radomes. If you have the impression that fi breglass is reserved for making rowing boats, it may be time to take another look at what else it can achieve. Fibreglass has a very good ultimate
tensile strength, higher than most metals. It’s a great insulator, with a very low coeffi cient of thermal expansion, and it is corrosion and weather resistant. For example, the ITER fusion reactor, a tokamak style fusion reactor being developed by 35 collaborating nations, uses fi breglass composite pre-compression rings (PCR) to hold the reactor together. T e ITER fusion reactor uses the PCRs to absorb the deformation and fatigue from magnets that hold the plasma, which is heated to 150,000,000 °C, in place. Fibreglass was selected for the PCRs because of the material’s specifi c high-performance mechanical properties. Fibreglass has withstood the test of
time. Since its early uses in World War II, the material has yet to be replaced with a better alternative. T is is largely due to the material’s mechanical properties combined with its competitive cost and design fl exibility. With composites, it is also important to note that the choice is not binary. Exel Composites off ers a range of pultruded and pull-wound composite solutions. It manufactures many carbon fi bre products along with fi breglass and hybrid combinations, where it uses both carbon and glass fi bres.
Deciding on the best material
choice requires a clear understanding of the desired application and product specifi cations, and the company fi rst works with customers to develop a mutual understanding. Based on this understanding, the composites supplier should use its materials science expertise to design the end user’s ideal composite product. T is discussion should include costs, particularly as raw carbon fi bre materials come at a higher cost point than fi breglass. Tailoring a composite can range
from a specifi c mix of fi bres to give certain properties, to managing the fi bre alignment and resin formulation. For example, a fi breglass tube could require extra reinforcements along one side of the geometry. In this case, carbon fi bres could be strategically incorporated into the tube along with the fi breglass at the point of manufacturing to create a strong hybrid structure that meets design requirements while considering cost optimisation. Having the correct tool at your disposal
is important whether you are trying to prune a bonsai tree or upgrade a piece of infrastructure. Although it may seem more appealing to use a chainsaw, or carbon fi bre, lower-key choices can sometimes be the better option for the task at hand.
Kim Sjödahl is senior vice president, R&D and Technology at Excel Composites.
www.exelcomposites.com
www.engineerlive.com 37
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