Shape-shifting carbon fibre could replace mechanical systems for planes and more

https://www.kth.se/en/aktuellt/nyheter/kolfiber-byter-skepnad-med-elektricitet-1.982298 

https://www.pnas.org/content/117/14/7658

Press release

A new carbon fibre composite material which can be bent with electronic impulses was demonstrated in a recent proof-of-concept study.

Published May 07, 2020

Imagine wind turbine blades that change shape to achieve the most efficiency in varying wind speeds, or airplane wings that bend and alter their own form without hydraulic rudders and ailerons. These are two potential uses for a carbon fibre material unveiled by researchers in Sweden.

Capable of changing form with the help of electronic impulses, the new solid state carbon fibre composite was demonstrated by researchers from KTH Royal Institute of Technology, in a proof-of-concept study published recently by Proceedings of the National Academy of Sciences of the United States of America (PNAS).

Co-author Daniel Zenkert says the material exhibits all of the advantageous properties of shape-morphing material – without the drawbacks that have prevented other development work from taking flight, such as weight and insufficient mechanical stiffness.

State-of-the-art morphing technologies, which can be used in robotics and satellite booms, rely on systems of heavy mechanical motors, hydraulic and pneumatic pumps, or solenoids to create shape changes, Zenkert says. These mechanically complicated systems add what is known as "parasitic weight" and are costly to maintain.

One way to reduce the mechanical complexity is to use solid-state morphing materials, he says.

"We have developed an entirely new concept," Zenkert says. "It's lightweight, stiffer than aluminum and the material changes shape using electric current." The material is capable of producing large deformations and holding them with no additional power, albeit at low rates, he says.

The composite consists of three layers – two of which are commercial carbon fibre doped with lithium-ions on each side of a thin separator. When the carbon fibre layers each have an equal distribution of ions, the material is straight. As electric current is added, the lithium ions migrate from one side to the other causing the material to bend. Reversing the current enables the material to return to a state of equilibrium and regain its previous, unbent form.

"We have for some time worked with structural batteries, such as carbon fiber composites that also store energy like a lithium-ion battery," Zenkert says. "Now we have further developed the work. We expect it lead to completely new concepts for materials that change shape only by electrical control, materials that are also light and rigid."

The researchers are now moving forward with other lightweight and structural materials that use less energy during use, with the ultimate aim of resource efficiency and sustainability.

Peter Ardell/David Callahan

Shape-morphing carbon fiber composite using electrochemical actuation

Wilhelm Johannisson, Ross Harnden, Dan Zenkert, Göran Lindbergh

Proceedings of the National Academy of Sciences Apr 2020, 117 (14) 7658-7664; DOI:

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