Aircraft Gets Self-Healing System

Taking cue from self-healing powers of plants and animals, experts are working on aircraft that will be able to fix damages on their own, that too in mid-air.

If the technique pans out, then aircraft, wind turbines and perhaps even spaceships of the future may boast of embedded circulatory systems with an epoxy resin that can bleed into holes or cracks and then fluoresce under ultraviolet light to mark the damage like a bruise during follow-up inspections, reports MSNBC.

The system could be a particular boon for lightweight, plastic-based composites known as fibre-reinforced polymers. Such polymers have recently grown in popularity with aircraft, spacecraft, automotive and wind-turbine manufacturers, who use the materials like protective layers of skin.

"Their Achilles heel is that they are quite susceptible to damage that is often undetectable to the eye," said Ian Bond, an aerospace engineer at Bristol University in the United Kingdom. "Users of composites spend a lot of time trying to detect this damage and worrying about what happens when it grows."

With funding from the Engineering and Physical Sciences Research Council, Bond and his collaborators have set out to compensate for the flaw with hollow glass fibres inspired by biological systems. "Most natural materials have an ability to heal and look after themselves when they're damaged," he said. With a similarly arranged network of vessels at vulnerable spots like the underbelly, doors, hatchways, wheel wells and wing bottoms, he reasoned, so might an aircraft.

At its base, the hierarchical system his team designed boasts of a two-part epoxy system. The epoxy and a hardener fill adjacent hollow glass fibres that, when broken due to a debris strike or other damage, release their contents and mix to form a plug, somewhat akin to clotting blood. Matched pairs of those filled glass fibres are arranged within the plane's structural skin, a larger network of carbon fibres embedded in stacked layers of plastic.

Although Bond's team has yet to test its self-healing system on aircraft, the epoxy network has performed well in standard "drop-weight tests" designed to simulate the effect of a dropped tool or kicked up runway debris. After the impact, tests suggest the bleeding epoxy can restore between 80% to 90% of the damaged surface's original compression strength.