Being developed for the new Boeing 787 aircraft and the Boeing 747-8, the GEnx is the most fuel efficient, quiet, and low-emissions jet engine that GEAE has ever introduced for large jet aircraft. One of the reasons for the GEnx engine's efficiency is its braided jet engine fan case by A&P Technology.
Like metal, a braid with an isotropic architecture provides properties that are the same in all directions. These isotropic layers of braid provide better impact and better fatigue properties than other materials while greatly reducing manufacture times.
In a typical woven tape lay-up, layers are stacked one on top of another to tailor the properties of the laminate to best withstand the loads to which it will be subjected. This mismatch of individual ply stiffness results in a variance in layer stress and strain that causes the laminate to fail in such a way that post-impact load-carrying ability is greatly reduced.
With braid, however, this mismatch between plies does not occur. The interwoven fibers within each layer of braid, which distribute load evenly, along with the isotropic architecture offered within each individual ply, provide braid with a unique resistance to crack propagation. Since each ply is isotropic within itself and identical to each neighboring ply, any interlaminar stresses are minimized during response to an impact event and the crack growth is contained to an area substantially smaller than those found upon impact of a much-heavier aluminum case.
These containment properties have been proven with the GEnx engine fan case by GEAE. In this case, the use of braid provides 30% better containment properties along with a weight savings of 350 pounds per engine, or 700 pounds in the case of a twin-engine aircraft. With braid, the weight of the twin-engine installation and retention features can be further reduced by as much as 100 pounds.
This increase in performance, combined with substantial weight savings, is the reason braided composites are playing an increasingly significant role in the manufacture of primary and impact critical aircraft structures. These structures include airplane frames, fuselage skins, airfoil cases, flaps, and ailerons.