18 June 2004
18 June 2004
In May 1954 the world’s first film adhesive for aircraft structural bonding was created.
The Redux Liquid/Powder system had been invented in 1942. This groundbreaking discovery was a long-awaited solution for bonding early fibre-reinforced composites.
Redux 775 Film was a further development of the Redux Liquid/Powder system, invented by Aero Research Ltd founder, Dr Norman De Bruyne and George Newell. It is still manufactured today at the same Duxford, UK site at which it was conceived (now part of Hexcel).
The Redux Liquid/Powder system was readily accepted by the aerospace industry and the first bonded structural components in an aircraft successfully completed their maiden flight 60 years ago, in July 1944. The aircraft was the De Havilland Hornet (and the Sea Hornet), whose wing structure relied heavily on ‘Reduxed’ wood/metal components. Experiments on converting the liquid/powder system into a film adhesive began in 1953. A so-called half-web was produced where a film of the liquid resole was coated onto polyethylene film, powder was applied to the phenolic coating and the excess was allowed to drop off, leaving a film which, by natural pick-up of powder, had the required liquid to powder ratio. Two half-webs were then consolidated together – powder face to powder face – to produce the Redux Film.
Redux 775 Film had the same adhesive properties as the original Liquid/Powder system, with the added advantage of it being supplied in a more user-friendly, handleable form. The first aircraft to be built with Redux 775 Film were the Handley Page Herald, Hawker Siddley 125, Armstrong Whitworth Argosy, Bristol Britannia, Sud Aviation Alouette and SAAB’s Lansen and Draken aircraft. Although the product line has been rationalised, Redux 775 Film has been used on a continuous basis since the 1960’s, particularly by the European aerospace industry.
A sample of the original batch of Redux 775 Film has been preserved, at ambient temperature, and tests have been carried out over the years using lap-shear performance to determine the effect of ageing on the film. Results show that there had been negligible deterioration in lap-shear strength over the 50 years. One final set of lap-shear tests was carried out on June 7th on metal joints bonded with the remaining sample of adhesive. Hexcel was delighted that average results of 29.5 MPa were achieved from the original batch of 50-year old adhesive.
Research into adhesives for aerospace and industrial markets is still a key focus for Hexcel, who recently launched a range of paste adhesives to complement the Redux films.
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