Fuel Cell Basics

What are they made of?
Fuel cells are an assembly of polymers, coated fabric materials, metal items and fittings. The materials used for the body of cells were selected for their flexibility and resistance to chemicals, adverse atmospheric conditions and abrasion. Initially Nylon was used, then Buna-N or Nitrile rubber, and finally Urethane. A cell wall may consist of layers of one of these materials and or a coated fabric for structural support and puncture resistance.

Goodyear built the original civilian fuel cell. They called it a “ Pliocel”. The process of making a Pliocel was an early version of tseamless multi-ply construction. This construction consisted of one to two layers of nylon woven fabric laminated with two to three layers of transparent nylon coatings. They were state of the art in the early 40’s and were installed in such planes as the Culver, Luscombe, Aeronca, Grumman and Sikorsky. Historically, they have been fairly resilient, however age, increased aromatic and chemical content in fuels, and the innate limitations of early technology have caused the Pliocels to become extremely brittle and begin to leak at flex points.

As synthetic rubbers such as Nitrile were developed, they gained widespread use in the petroleum industry and quickly became the dominant material for fuel cells in the 1940’s. During World War II, the use of nitrile greatly increased due the demand for sealing tanks in fighters and bombers. Original Equipment manufacturers(OEM’s) such as US Rubber, Uniroyal, Firestone, BF Goodrich and others have used nitrile rubber almost exclusively.

Goodyear eventually abandoned the Pliocel process in the mid 60’s with the advent of urethanes. They have remained the leader in urethane fuel cell technology ever since. Now Engineered Fabrics Corporation (formerly Goodyear Aerospace) is the largest OEM for most general aviation, commercial and military aircraft.

How are they Made?
Most cells have three basic layers; an inner liner, a fabric structural support with vapor barrier coating and an outer protective layer. The three basic layers are usually calendared at the fabric mill into a single sheet of coated fabric.


A ply is either a sheet of coated fabric, sheet of rubber or a layer orubber coating. However, coatings of glues or other materials are not considered plies. Several plies may be used. All cells are manufactured using one, two or multiple plies of polymer materials.

One-ply constructions are laid up with one ply of coated fabric. The fuel cell manufacturer lays the coated fabric from the mill over a form and glues the seams. One-ply lay-ups use clever overlap configurations to try and avoid seam leaks.

Two-ply cells are laid up with two separate plies of coated fabric and sheet rubber. These plies overlap for increased sealing at seams and corners. This method is less problematic but can still be susceptible to channel leak issues. Both of these lay-ups can be made with cured or uncured material and then cured (vulcanized) with heat and pressure.

There is also the multi-ply lay-up method that combines coatings, sheet goods and coated fabric plies with proper multiple overlaps to produce a seamless cell basically eliminating seam and channel leak issues. This method requires increased building time and material cost but far exceeds the other methods in quality, defect reduction, flexibility and appearance. Examples of this method are the Goodyear / Engineered Fabrics urethane constructions, the US Rubber mil. spec. nitrile constructions and Eagle’s EMS7 nitrile construction.

A typical nitrile rubber fuel cell is made by “laying up” uncured rubber, rubber parts and sheet goods over a disposable corrugated cardboard form.

Then cured or “vulcanized” under heat and pressure in an autoclave.

The form is then soaked with water and removed.

The metal rings are attached and plated for testing.

Finished cells waiting to be inspected, and weighed.