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. 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 1990s. During the closed mould curing process the thermoelastic behaviour of the foam core provides internal pressure, consolidating even thick prepreg layers against the mould surface. Due to the inherent creep compression resistance, these foam cores provide high and constant pressure, and pressures of up to 7 bars (100psi) can be reached and maintained during the cure cycle.
The main blade of AgustaWestland’s EH101 helicopter is one of the most impressive examples of such a modern blade in series production, with a blade length of pproximately 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.
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