Snecma prepares dual fan factories for Leap engines

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By 2019, Snecma will be producing one composite fan blade for the CFM International Leap engine every 30 minutes, or 32,000 per year, from two identical manufacturing centres of excellence, one in the US and one in France, say company officials.

Preparations for the production ramp up are in full swing, accentuated by the end of June design freeze for the Leap-1A and Leap-1C engines for the Airbus A320neo and Comac C919, respectively. Design freeze for the Leap-1B, which will power the Boeing 737 Max, will occur next year. Snecma is responsible for the fan and low-pressure sections of CFM engines while joint venture partner GE builds the high pressure components.

Following the Farnborough air show, CFM is reporting a total of 3,752 orders for the new engines with 922 orders valued at $12.6 billion received in recent weeks.

Snecma will be constructing the blades and three other resin transfer mould (RTM) parts for the Leap engine - the fan case, a platform between the blades and a spacer for underroots of the blades - in partnership with New Hampshire-based Albany Engineered Composites, a company that specialises in woven composite technology for paper mills.

The RTM technology, which Snecma spent about $200 million and 15 years developing, involves carbon fibres that are woven together in an interlocked 3D matrix that is then injected with resin to form a composite part.

"RTM gives a higher damage tolerance capability," says Jean-Jacques Orsini, design office manager of fans and compressors for Snecma. "With the 3D, you have a weaving structure that has significant damage tolerance capability for bird impacts and debris. Think about it as a piece of clothing woven in 3D."

The first 31,600m² (340,000ft²) plant, in Rochester, New Hampshire, will be operational in mid-2013, followed by an identical plant in Commercy, France, one year later. Each will be staffed by 200 Snecma employees and 200 Albany employees. Snecma will own both plants and lease space to Albany, which will be under a services contract to Snecma.

Machinery at the plants includes looms where the carbon fibres are woven into the fan blade and fan case preforms. After weaving, the blade pre-forms are cut out using a water jet, leaving approximately 0.3m of excess material around the outline. Orsini says in future Snecma will look to minimise the residual material, but it is not a concern at this time.

Next the blade pre-form is inserted into two-sided mould into which epoxy resin is inserted at 8.6bar (125lb/in²) over a 6-7min period with the mould heated to 360°F. The blade is cured for 5h in the mould. Technicians then use a five-axis tool to machine the blade to the correct dimensions, perform a check of those dimensions, then bond the titanium leading edge to the blade, coat it with black paint and perform non-destructive inspection (NDI) to determine the leading edge bond characteristics and the internal blade integrity.

For fan cases, the preforms are wrapped four-times around a mandrel with a resin injection system and the entire mandrel placed in an autoclave for curing. Snecma says it is investigating an out-of-autoclave process similar to that of the blade to make the process more efficient and faster.

Albany employees will be responsible for weaving the preforms, cutting the preforms to shape, injecting the resin and curing the part; Snecma will perform final machining and painting of the parts.

Snecma to date has built 500-600 blades and numerous fan cases and other RTM parts in a temporary manufacturing facility in Albany's Rochester plant, where engineers have been experimenting with different weave patterns.