Bristol: Self-repairing aircraft could improve aviation safety

Commercialisation opportunity

Researchers at Bristol University, UK, have developed a new technique that mimics healing processes found in nature enabling damaged aircraft to “mend” themselves automatically, even during a flight. 

Apart from improving safety this could make it possible to design lighter aeroplanes, leading to fuel savings, cutting costs for airlines and passengers and reducing carbon emissions.

The researchers have set themselves an ambitious target of four years to commercial exploitation, and are looking for investors and companies looking to co-develop the technology. “This will require significant investment and industrialisation but could be achievable,” lead researcher Ian Bond told Science|Business.

The technique involves embedding epoxy resin in reservoirs in the aircraft body. If a tiny hole or crack occurs due to wear and tear, fatigue, or a stone striking the aircraft, the resin would ‘bleed’ out and quickly seal it up, restoring structural integrity. By mixing dye into the resin, any such self mends would show as coloured patches that could be pinpointed during subsequent ground inspections, and a full repair carried out if necessary.

The technique has been developed by aerospace engineers at Bristol University, with funding from the UK Engineering and Physical Sciences Research Council. It has potential to be applied wherever fibre-reinforced polymer (FRP) composites are used. Such materials are in increasing use not only in aircraft, but also in car, wind turbine and spacecraft manufacture.

“This approach can deal with small-scale damage that’s not obvious to the naked eye but which might lead to serious failures in structural integrity if it escapes attention,” says Bond. “It’s intended to complement rather than replace conventional inspection and maintenance routines, which can readily pick up larger-scale damage, caused by a bird strike, for example.”

By further improving the safety characteristics of FRP composites, the self-healing system could encourage even more rapid uptake of these materials in the aerospace sector. Aircraft designs including more FRP composites would be significantly lighter than the primarily aluminium-based models currently in service. Even a small reduction in weight equates to substantial fuel savings over an aircraft’s lifetime.

“This project represents just the first step,” says Bond. “We’re also developing systems where the healing agent isn’t contained in individual glass fibres but actually moves around as part of a fully integrated vascular network, just like the circulatory systems found in animals and plants.”

Such a system could have its healing agent refilled or replaced and could repeatedly heal a structure throughout its lifetime.

The team is working with industrial partner Hexcel Composites Ltd, a manufacturer of composites for aerospace and other industrial applications.

The resin used in the self-repair system is an off-the-shelf, Araldite-like substance. The team are currently developing a custom-made resin optimised for use in the system.