Send this page / Print this page Home / Composites News / Applications

31 Jan 2007  -  United Kingdom

Advanced helicopter rotor blades

Already in 1971 ROHACELL® PMI foam received the first specifications as sandwich core material for an advanced helicopter part. 

In the 1990s Westland Helicopters (now AgustaWestland) introduced PMI foam into the British Experimental Rotor Program (BERP 1) aiming for the development of a new generation of advanced helicopter rotor blades. The first flight of a Lynx AH MK 9 fitted out with the new advanced composite blades took place in 1989. The rotor diameter was 12,8m / 42 ft. 

At present the manufacturing of high performance advanced helicopter rotor blades using ROHACELL® structural sandwich cores is state-of-the-art technology. The initial change from old metal blade design to composite blades was prompted by the desire to solve corrosion problems and to meet the demand for increased performance and service life of the blades. The manufacturing method using PMI foam cores as an "active" mandrel and structural part of the component was developed in a close cooperation between Westland Helicopters and the ROHACELL® engineering team in the late nineteen nineties. Until today the technology principle is well known as In-Mold Pressure Process. 

During the closed mould curing process the thermoelastic behaviour of the foam core provides internal pressure, perfectly consolidating even massive prepreg layers against the mould surface. Owing to the excellent creep compression resistance, such foam cores can provide a very high and constant level of pressure. In mould pressures of up to 7 bars (100 psi) can be reached and maintained during the cure cycle. The desired peak pressure can be adjusted to precisely meet the gel point of the epoxy prepreg. 

The high level of mechanical properties of the foam improves buckling resistance of the mostly very thin U-spars used in blade design. Due to outstanding fatigue bahavior, which is not second to any other rigid foam, PMI foams withstand the high dynamic loads to which the rotor blades are exposed during their service life. Using ROHACELL® - foam-cored design made it possible to achieve a quantum leap in service life of helicopter rotor blades. 

The main blade of AgustaWestland's EH101 helicopter is probably the most impressive example of such a modern blade in series production. The length of the blade is approximately 8,5 metres. Most recently the first flight of an EH101 helicopter equipped with the latest state-of-the-art composite blades using ROHACELL® structural foam took place. This new high-performance rotor blade is the result of the British Experimental Rotor Program (BERP 4) program.

Source : Degussa