British researchers develop technique that enables an aircraft to ‘repair itself’

Friday, June 20, 2008, 19:38 by Aviation Correspondent

A revolutionary technique that would enable a damaged aircraft to “repair itself,” even during a flight, has been developed. This breakthrough mimics the healing processes found in nature, the website sciencedaily.com has reported.

Besides the principal advantage of safety, the “self-repairing” technology could lead to design of lighter aircraft in future. The novel design would mean saving on fuel, cutting of costs for airlines as well as for passengers and reduction in carbon emissions. This simple technique that can be used by the so called self-repairing aircraft is similar to the healing processes that take place after a person cuts himself, according to website.

The ingenious method of an aircraft repairing itself  – developed by aerospace engineers at the University of Bristol, the United Kingdom, with funding from the Engineering and Physical Sciences Research Council (EPSRC) – works like this: If a tiny hole/crack appears in the aircraft (for example, due to wear and tear, fatigue, or a stone striking the plane), epoxy resin would “bleed” from embedded vessels near the hole/crack and quickly seal it up, restoring structural integrity. By mixing dye into the resin, any “self-mends” could be made to show as coloured patches that could easily be pinpointed during subsequent inspections of the aircraft on the ground, and a full repair carried out if needed.

The ground-breaking technique where an aircraft can heal itself even while in flight can be effectively applied wherever fibre-reinforced polymer (FRP) composites are used. (Fibre-reinforced polymer composites are lightweight, high-performance materials that are proving increasingly popular in the manufacture of aircraft, car, wind-turbine and even spacecraft).

In the novel technique, the hollow glass fibres contained in FRP composites are filled with resin and hardener. If the fibres break, the resin and hardener ooze out, which enables the composite to recover up to 80%-90% of its original strength. The result is that the aircraft can still function well at its normal operational load.

Dr Ian Bond, who led the project at the University of Bristol, was quoted by the website sciencedaily.com as explaining: “The new approach can deal with small-scale damage that is not obvious to the naked eye but which might lead to serious failures in structural integrity if it escapes attention. It is 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.”

One offshoot of the “self-healing” technique for aircraft is that, that by improving the excellent safety properties of FRP composites further, the self-healing system could promote larger use of FRP composites in the field of aerospace. Aircraft that use more of FRP composites would be considerably lighter than aircraft designs that primarily rely on aluminum-based models.

The researchers at the University of Bristol are of the opinion that even a small reduction in weight would translate to substantial savings in fuel over an aircraft’s lifetime.

“This project represents just the first step,” Ian Bond elaborated. “We are also developing systems where the healing agent is not 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. Furthermore, it offers potential for developing other biological-type functions in man-made structures, such as controlling temperature or distributing energy sources.”

The researchers claim that the “self-repair” technique developed at the University of Bristol could be available for commercial use in about 4 years.

The research project, lasting 3 years and titled Bleeding Composites: Damage Detection and Repair Using a Biomimetic Approach, concluded by the end of April 2008.

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