Shape-shifting carbon fibre composite
A new solid-state carbon fibre composite is capable of changing form with the help of electronic impulses, say researchers from KTH Royal Institute of Technology in Sweden. It is envisaged the material could create wind turbine blades that change shape for optimum efficiency in varying wind speeds, or aeroplane wings that bend and alter without hydraulic rudders and ailerons.
The composite is made up 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. When electric current is applied, the lithium ions migrate from one side to the other causing the material to bend. Reversing the current allows the material to return to a state of equilibrium and regain its previous, unbent form.
Co-author of the paper, Dan Zenkert, says the material exhibits the advantageous properties of a shape-morphing material – without the drawbacks that have prevented other development work from taking flight, such as weight and insufficient mechanical stiffness.
He notes that 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, These mechanically complicated systems, he says, add parasitic weight and are costly to maintain. One way to reduce the mechanical complexity is to use solid-state morphing materials.
Zenkert adds, ‘We have for some time worked with structural batteries, such as carbon fibre composites that also store energy like a lithium-ion battery. Now we have further developed the work. We expect it can lead to completely new concepts for materials that change shape only by electrical control, [and] are also light and rigid.’