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Whatsapp A technician works on the wing of an Airbus A320 during construction at the Airbus SAS factory in Broughton, England

Australian science might be experiencing a crisis of confidence, but our scientists certainly aren’t suffering a creativity deficit. Antony Funnell meets the Melbourne aeronautics engineer who’s busy redefining the motto ‘heal thyself’.

Imagine a self-healing plane—an aircraft with an outer shell that can mimic the regenerative powers of skin and repair itself in the event of cracking.

Researchers at RMIT in Melbourne have been working with high-tech carbon fibre composite materials to create just such a system.

Carbon composites are increasingly being used by major aircraft manufacturers like Airbus and Boeing because they offer greater flexibility and aerodynamic versatility than traditional aluminium sheeting. The wings and fuselage of the new Airbus A350, for example, are now primarily made from a polymer material reinforced with a mesh of carbon fibre.

Essentially you can put in sensors, and these detect changes in the electrical resistance. When it cracks, the resistance will go up.

They also have a superior strength-to-weight ratio, which allows manufacturers to construct a lighter, more fuel-efficient aircraft without compromising safety.

As with any form of structural material, however, carbon fibre composites are subject to wear and fatigue, and that deterioration can include stress fractures.

The peculiar difficulty with laminated polymer sheeting, according to RMIT’s Chun Wang, is that when cracking does occur, it often happens inside the sheeting and is difficult to visually detect.

In response, Professor Wang and his colleagues at the Sir Lawrence Wackett Aerospace Research Centre have developed a new structural material that comes with its own inbuilt repair kit.

It works like this: micro-sized capsules of polymer are embedded throughout the carbon fibre sheeting so that when a crack develops, the embedded pellets directly around the fracture melt and flood the fissure with resin, effectively fusing the material back together.

‘What we've been looking at is a different polymer that is thermoplastics based,’ says Professor Wang, who acknowledges that his team isn’t the first to successfully develop such a technology. What makes the RMIT process notable, however, is that it can be replicated.

‘It is a special type of polymer that has an intrinsic property to react with the functional groups in the original composite,’ says Professor Wang. ‘So this additional reaction can produce drivers, like little vapours, that can propel the resin into small cracks.

‘This particular polymer has a multiple use purpose. If you break it, you heal it, you re-break it and you [can] re-heal it multiple times. The property retains its original performance over multiple cycles of this break/heal, break/heal event.’

The idea is that if an aircraft is suspected of experiencing fatigue, a fusing agent like heat could be applied to the plane’s carbon composite body in order to activate the restoration.

Laboratory tests have shown that a damaged piece of this new carbon composite material can be repaired up to six or seven times without what Professor Wang describes as a ‘noticeable reduction in performance’.

Professor Wang and his team are now experimenting with a more advanced system that would ultimately allow the process to be automated, eliminating the need for human intervention.

‘Essentially you can put in sensors, and these detect changes in the electrical resistance,’ he says. ‘When it cracks, the resistance will go up. By having the sensors you actually can detect them and subsequently inject a current into the structure, an electrical current. Those electrical currents can locally heat up the composite, so the heating can then be used to trigger the healing process.’

One major hurdle, though, concerns weight.

While carbon composite materials are relatively light, the inclusion of polymer pellets make the material developed by RMIT around 10 per cent heavier. Professor Wang admits that this could be an issue for aircraft manufacturers because any additional weight adds to fuel consumption and therefore operational costs.

‘What we will be looking to do [is] additional research to find the material that would not add to the weight; it can be actually part of the original structure. We want to use a material that has a blended structure that has got intrinsic material that can carry the load as it is and it has this healing functionality for repairs.’

Work on the system is continuing in collaboration with the Boeing Research Technology Centre in Melbourne. Professor Wang says there’s still considerable refining to be done before the new material will be ready for commercialisation.

Flight of fancy Listen to the full episode of Future Tense as Antony Funnell traces human flight from the days of wood, canvas and bicycle chains to the supersonic Concorde.

Exploring new ideas, new approaches, new technologies—the edge of change. Future Tense analyses the social, cultural and economic fault lines arising from rapid transformation.



