FiberSkyn is the trademarked name of a synthetic plastic material in sheet form that is used in the manufacturing of drum and banjo heads by an American company called Remo.
Fiberskyn consists of two layers glued together, PET film and Tyvek. The Mylar provides strength, while the Tyvek adds thickness, a less synthetic sound, and an appearance reminiscent of animal skin.
References
FiberSkyn Wikipedia(Text) CC BY-SA