Portsmouth, UK - GKN Aerospace claims to have developed the first single-skin flexible fuel-bladder material for aircraft tanks that offers both crash resistance and puncture tolerance.
The group said the move is part of an initiative to reduce or remove volatile organic compounds (VOCs) from the manufacturing processes for fuel tanks. GKN launched the development at Heli-Expo in Houston, Texas, in February.
The material consists of a sandwich of three layers of polyurethane, interspersed with a layer of aramid for puncture protection, and a special fuel barrier layer (see picture).
Frank Bamford, senior vice president of business development and strategy estimates that, "use of this material could lead to a 60-percent reduction in the use of VOCs and a 30-percent reduction in manufacturing times." Each fuel bladder could also weigh about 5 percent less, since the adhesive coatings used in traditional bladder construction have been eliminated, GKN adds.
Traditionally, aerospace fuel bladders have used multiple layers of composite materials, with solvent-based adhesives used to join the bladder to protective textile layers - requiring adhesives and a final lacquer coating to protect the bladder exterior.
In the new construction, a thermoplastic polymer replaces the traditional nitrile rubber: the crash-resistant textile is incorporated within the polymer. The material also contains an integral fuel barrier to provide the same level of fuel tolerance as traditional tanks.
No adhesive is needed for the crash-resistant layer, and no final lacquer coating is required, significantly reducing VOC use.
Additionally, fuel tanks can be welded into shape using radio frequency waves, without adhesives or solvents, because the material is based on polyurethanes.
"… our R&D effort in all our businesses is targeted on developing and applying new technologies to bring real and practical benefits to aerospace," Bamford commented, in the company statement.
This new material is "a huge progression" in flexible transport of fuel for helicopter operators and others, he added.