The growing interest for 3-D wovens in the aerospace market
CFM International, a joint-venture between General Electric Aviation and Snecma, recently became the first company to successfully integrate 3-D woven composite parts into aerospace engine designs. The new engine, known as Leading Edge Aviation Propulsion (LEAP), demonstrates that 3-D wovens are not only a viable option for metallic engine part substitution but also can replace other metal and 2-D composite materials in a variety of applications.
As the name suggests, 3-D woven composites are fiber textiles characterized by their three-dimensional yarn orientation. They are reinforced in multiple directions, including the through-thickness direction. Unlike conventional laminate composites, which are typically only reinforced in the plane of the laminate, 3-D wovens can exhibit different material properties throughout a single component. For instance, a component might have increased axial stiffness in one area and greater shear strength in another.
3-D fiber textiles are constructed using traditional textile weaving techniques to create advanced preimpregnated fibers (prepreg) that interlace multiple fiber layers across the horizontal and vertical axes. Since the fabric can be altered during the weaving process, the material can include smart sensors and stronger fibers depending on the needs of the composite part. According to Alistair McIlhagger, Ph.D., senior lecturer at the Engineering Research Institute at the University of Ulster in Belfast, Northern Ireland, the implications of this material advancement could mean large-scale change for the use of composites across major commercial markets such as automotive, wind and aerospace.
LEAP Demonstrates Successful Integration
CFM International established the LEAP project in 2005 to develop a successor engine for its CFM56 family of airplane engines. One focus for the project was to use a 3-D woven resin transfer molding (RTM) process developed by Snecma, a French aerospace engine manufacturer, to create an even more aerodynamic composite fan. The fan blade design went through numerous iterations. The finished engine fan – including 18 engine blades, a disk and fan case – features 3-D material that is woven and manufactured by Albany Engineered Composites (AEC), Rochester, N.H.
To manufacture one LEAP engine fan blade, AEC weaves miles of carbon fiber using a continuous spooling process in large industrial jacquard looms. AEC weaves and cuts the preforms, injects the resin and cures the part using a patented RTM process. Once the initial preform is shaped, the company cuts the blade into the desired shape using water jets. The material is then injected with resin in a heated mold. The entire process takes 24 hours to complete. Snecma is then responsible for the final machining and painting of the parts that CFM International distributes to aerospace companies.