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Rohacell® PMI foam was specified for the first aircraft applications back in 1971, on the Eurocopter Ecureuil EC120 helicopter. Today, approximately 1,800 individual parts on the BK117, EC 120, EC 135, Tiger, and NH90 aircraft incorporate high-performance Rohacell® foam cores.
(Published on December 2005 – JEC Magazine #21)
The Rohacell® engineering team worked in close cooperation with a major European helicopter manufacturer to develop a manufacturing method that would use PMI foam cores as an “active” mandrel and structural member of the sandwich component. More cost-effective than honeycomb, using the foam-cored design increased the service life of rotor blades from approximately 400-500 flight hours for the initial metal blade to more than 10,000 flight hours today.
A detailed study carried out by Bell concluded that a PMI foam-cored tail rotor blade costs only about 20% as much to manufacture as the honeycomb-cored version. This is because the foam core makes it possible to introduce a single curing process, whereas the honeycomb core requires several curing and bonding operations. In addition, machining of the foam core is much easier, and feed rates up to ten times higher are possible. PMI foam cores have been introduced successfully in many major blade programmes. With a length of approximately 8.5 metres, the main blade of Westland’s EH101 helicopter is probably the most impressive example.