How surface chemistry is unleashing the full potential of carbon fibres
Carbon fibre is one of the strongest materials in the world but with its strength comes limitations, particularly when it comes to its functionality.
But this is now changing. IFM’s surface chemistry and interface team has a growing body of research that is expanding the use of carbon fibres by imbuing the material with tailored functionality – from changing its colour to giving it the ability to absorb and store energy – using reliable, scalable and rapid surface modification techniques.
‘We have given carbon fibres new and previously-thought-impossible functionality,’ says team leader Professor Luke Henderson.
‘The surface of carbon fibres is quite inert and very little will react with it, to the detriment of the final material.
‘Our focus is the development and implementation of surface modification techniques that allows us to install a chemistry on the fibre surface that is for a specific application. At the moment it’s a “one-size-fits-all” approach.’
So far, the team has had their work funded by industry partners such as Boeing, SABIC, Solvay, Fortescue Metals group, Rolls Royce, Ford USA, Gen2Carbon (formerly ELG carbon fibre) and CASS Foundation, as well as Australian Government funding bodies such as the Australian Research Council.
Already, the team has made significant discoveries.
Carbon graphite is black and in the past, there were only two ways to change the colour of carbon fibres – either painting the surface or weaving the fibres with a dyed fabric.
In their discovery, the team made modifications to the fibre that turned the carbon fibres an electric blue colour.
‘The real kick is that it works by the same mechanism as nature’s way to generate blue colours,’ Prof. Henderson says.
‘Blue in nature is very hard to generate with a pigment – what it does is it actually uses the wavelengths of light to interact with each other.
‘It’s the same way that butterflies and peacocks generate their iridescent blue. So we went with a bio-inspired colour generation theme rather than a pigment approach.’
Through their study, the team found further benefits to the surface modification. In addition to now being able to change carbon fibres to a variety of colours, the treatment also makes the material stronger and stiffer – in some cases up to 30 percent in tensile strength – a strength improvement via a treatment that Prof Henderson says is unheard of.
‘This is beneficial, because a carbon fibre that is stronger and stiffer, yet still light-weight, significantly increases its value,’ he says.
‘We have also found that because our material is effectively coated in a polymer, it has the ability to be moulded and bear weight under no tension – and that’s not really possible.
‘This means that moulding it to different shapes is possible. Normally, if you have a mould and you put a carbon fibre fabric inside it and you mess up a section, you have to throw it out.
‘But with our material you can just put some acetone on it, weaken the polymer, remould it and you are good.
‘This could make manufacturing a bit easier and save costs on things like wastage.’
In another study, the team was engaged by Barwon Health to modify the surface of metallic joint replacements to allow natural polymers, such as silk, to adhere to them for drug delivery.
‘Silk can be turned into a plastic-cling-wrap-type material that’s actually quite durable and strong,’ Prof. Henderson says.
‘What surgeons at Barwon Health wanted to do was put a layer of silk on top of a joint implant, like a hip replacement, and load it with antibiotics.
‘What happens is as your hip heals, the silk degrades and releases that antibiotic to minimise the infection around the local environment.
‘This has the potential to work well because bone is very poorly impregnated by antibiotics.
‘The main problem is that the materials that are used for joint replacement are titanium and stainless steel, and silk does not adhere to them at all.
‘Our project is on how do we modify the surface of the metallic implant to adhere to silk so that it doesn’t flake off?’
The team has already produced a paper on their early results, which show promise – researchers have already found a way to effectively use the silk as an adhesive between two metals with outstanding strength results.
The team is also conducting major research projects with the US Department of Defense’s research arms: the Air Force Office of Scientific Research; the Army Research Laboratory; and the Office of Naval Research Global.
‘For the US Army Research Laboratory we are developing materials that have energy absorbing capabilities, essentially blasts on armour,’ Prof. Henderson says.
‘What they require is light-weighting that can still withstand an ultra-high strain rate event.
‘They already have systems in place but how their systems work, they can’t really use carbon fibre to reinforce it because it is incompatible – that’s where we come in.’
The Air Force Office of Scientific Research has also engaged the surface chemistry team to conduct research on carbon fibres suitable for ultra-high temperature applications.
‘The problem with carbon is, for all its benefits, if you put it in a hot atmosphere in air it effectively degrades because it’s carbon and it degrades to CO2,’ Prof. Henderson says.
‘There are ways they are currently trying to treat the fibres to put them into a really high temperature, but it is very archaic, so they engaged us to see if we could come up with a smart way to develop carbon fibre for high-temperature applications.’
The team has also put in a new proposal to the Office of Naval Research Global to look at fibres that can be used to store energy.
‘It’s called structural energy,’ Prof. Henderson says. ‘Imagine a car or boat or plane that has the ability to store energy in a passive panel.
‘It could be the bonnet of your car and that might hold enough charge for your electric car.’
The team takes an interdisciplinary approach, which has unlocked fresh ideas and discoveries – an approach that stems from Prof Henderson’s own experience with interdisciplinary collaboration.
Prof. Henderson comes from an organic chemistry background – his PhD focused on the synthesis of molecules for medical applications.
He completed a Postdoc at Oxford University, where he conducted catalysis for GlaxoSmithKline and then went on to Deakin University as an Alfred Deakin Fellow developing new antibiotics.
‘I came into this area of surface chemistry, as a friend of mine asked my opinion as a chemist about a materials science problem – specifically about carbon fibre surfaces and their chemistry,’ he says.
‘From this interaction has come a huge volume of work from my group and this is now the primary focus of my research.
‘The key was that my perspective as a chemist is very different to that of a materials scientist and as such this interdisciplinary perspective has allowed us to do things people thought impossible only 10 years ago.’
At IFM, his team is made up of 15 researchers with expertise across chemistry, electrochemistry, analytical chemistry, biology, polymer science, aerospace engineering, nanomaterials, and photocatalysis. Of the researchers there are four postdoctoral fellows, eight PhD candidates, one Masters student and two honours students.
‘With the team having a range of expertise, it’s easy to call on someone and say, “what’s your knowledge about how this works?”,’ Prof Henderson says.
‘We’ve had experiences when an engineer has picked up on something on natural interfaces and decided to take it away and have a go at it and they’ve been able to provide that different perspective.
‘We’re trying to solve an historical problem in composites, which is adhesion.
‘Adhesion is everywhere, one example in nature is mother of pearl, or nacre, which is made of contradictory properties, basically properties that don’t usually go together and that’s because of how the hard and soft materials inside that material interact with each other at the interface.
‘That is what we are trying to do – we are trying to get to a more superior material through managing those interactions at a molecular level.’