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10 Aug 2020

MYTH-BUSTING; Is Aluminium Weak?

The yield and tensile strengths of aluminium varies from 30-500N/mm2 and 79-570 N/mm2, while for steel the figures are in the range of 250-1000 N/mm2 and 400-1250 N/mm2. That doesn’t means that aluminium is weak though. Depending on the alloy and processing technique, aluminium can be forged to be just as strong, if not stronger, than many types of steel.

In the construction sector, the 6000 series of alloys are generally used, which contain manganese and silicon alongside the aluminium. The most common amongst these is alloy 6061, which is hot rolled to achieve an impressive ultimate tensile strength of 262N/mm2 (42 KSI), easily matching many grades of structural steel.

However, there are plenty of high strength aluminium alloys which can even outperform steel. A 3cm thick wire made from a 7000 series alloys, for instance, which also contains zinc, would easily be able to suspend a fully-loaded tractor and trailer in the air.

When it comes to strength however, the key benefit of aluminium is that it is so much lighter and less dense than the equivalent sized section of steel – hence the fact that it is widely used in the automotive and aerospace industries, as well as in construction, where the strength to weight ratio is so critical.

Typically, aluminium weighs between 35% and 65% less than steel so can deliver the structural strength and stability required, but without either the volume or the bulk. For windows, doors and curtain walling applications, that is the reason why aluminium frames can achieve slimmer sightlines, maximum natural light and optimum solar gain.

When aluminium is used extensively throughout a building, the lighter weight can have a very significant impact beyond the aesthetics – from reducing the cost of foundations, to making it cheaper and easier to transport and handle materials on site. It is no coincidence that the first building to use aluminium extensively was New York’s Empire State Building, way back in 1931. It was the combination of strength and weight of the aluminium which made that original skyscraper a possibility for the first time.  Aluminium was used in all of the building’s basic structures and even in the interior, and it is still on view on the walls of the lobby.

When you compare the strength of aluminium with other materials such as PVC-U and timber, then the evidence is clear. Aluminium is routinely used as a reinforcement in PVC-U windows and doors to provide the strength and rigidity required, and it is both stronger and lighter than even engineered timber.

Safety and security are a given of course. Aluminium windows, doors and curtain walling can meet the most stringent testing and accreditation requirements, including PAS24 and SBD and, for structural applications, BS EN1999-1-1 and/or BS EN 1090-1.

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