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Aluminium nanofoams set to transform impact absorbers
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01/02/2007
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An Austrian company is leveraging nanotechnology control processes in the development of closed-cell aluminium foam, writes Roger Bishop. They can be formed into any shape and have huge potential for the automotive industry within a few years.
Metcomb Nanostructures of Schwarzenau says the material weighs about a fifth of conventional aluminium and has a uniform cell-to-cell chemistry that will bring consistent performance to systems using it. Principal applications are expected to be in crash management (side impact beams, crash boxes, knee bolsters and A/B pillar impact protectors) and structural systems (transverse links, engine mounts, casting cores for suspension parts and A,B,C pillar and sill reinforcements).
Metcomb has been developing its proprietary technology for around seven years and hopes the first vehicles using it will be on the road within five years.
Each cell is protected by a 10 to 90nm thick solid oxide skin derived from the gas used in the manufacturing process. This is critical to maintaining cell stability. The size of the cells can be varied depending upon density requirements.
The material’s isotropic properties enable it absorb energy regardless of impact direction and when the material is crushed it has a stress plateau. This, says Metcomb, makes it ideal for converting impact energy into deformation energy.
A letter of intent has been signed with Dr Ing Jog Wellnitz, professor of lightweight design at the University of Applied Sciences in Ingolstadt. Through this agreement the foam will be used for projects with development partners who include BMW, Audi and EDAG. Metcomb also is working with BMW to develop a stiffer and lighter engine mount.
A study on carbon nanotubes suggests they can act like ‘super-compressible’ springs, opening the door to foam-like materials for applications where strength and flexibility are needed. Films of aligned multiwalled carbon nanotubes can apparently flex and rebound in response to a force, maintaining their resilience even after thousands of compression cycles. Pulickel Ajayan, professor of materials science and engineering at Rensselaer Polytechnic Institute, said the nanotubes can be squeezed to less than 15% of their normal lengths by buckling and folding themselves like springs. They are also stable in extreme chemical environments, high temperatures, and humidity – all of which adds up to a number of possible applications, from flexible electromechanical systems to energy absorbing coatings.
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Author
Roger Bishop
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