Nanotube network could spot wing weakening

 作者:高衙剀     |      日期:2019-03-02 07:01:02
By Jeff Hecht Embedding carbon nanotubes within composite materials, like aircraft wings, could help spot structural flaws that would otherwise escape detection, researchers claim. Composite materials are made by weaving together strong fibres of carbon or glass and embedding them in a matrix of epoxy or other polymer. They are widely used in the construction of aircraft because they offer an unmatched combination of strength and lightness. Their downside is that internal defects that can lead to catastrophic structural failure can be hard to detect. Now engineers at the University of Delaware in the US have shown that carbon nanotubes embedded in composite materials can be used to spot these hidden internal flaws. Nanotubes are highly conductive. When dispersed, overlapping, through a composite they form a network that conducts electricity. These connections are tenuous, so any changes in the composite structure also changes the way the network conducts electricity. In tests, researchers Erik Thostenson and Tsu-Wei Chou found that monitoring the current transmitted through an embedded nanotube network can easily spot internal stress or damage to a composite, giving crucial advanced warning of possible failure. Optical fibres have previously been embedded within composite structures to monitor stress by observing changes in how they transmit light. But with diameters of 100 micrometres or more, optical fibres are much larger than those fibres found in composites. These are typically about 7 to 15 micrometres in diameter and make up 50% to 70% of the composite volume. If embedded in a composite, optical fibres will therefore weaken the overall structure. Measuring their light transmission also requires complex optical equipment. Thostenson says nanotubes provide a much better solution. “Multi-walled carbon nanotubes are 10 to 20 nanometres in diameter, three orders of magnitude smaller than [regular] carbon or glass fibres,” he says. Nanotubes also do not disturb the mechanical structures of the composite, and only a small amount are needed for sensing, adding up to 0.1% to the material’s weight, he adds. “This is something that can be used today,” Thostenson told New Scientist, because it requires only simple electrical measurements. Journal reference: Advanced Materials (DOI: 10.1002/adma.200600977) More on these topics: