Early development history of glass mat thermoplastic (GMT) sheet

Once upon a time, glass mat thermoplastic (GMT) composites were pretty much the only option for engineers looking to add stiffness, strength and toughness to polymer materials, with melt-reworkable matrices, moderate cost, industrial-scale production capabilities, and relatively thin sections. Filled and short fiber reinforced thermoplastics, mostly nylon, are limited to small nonstructural parts that can be injection molded.
  
GMT sheet, developed in the mid-1960s, provides molders with a compressible molding material with continuous random fiber reinforcement at moderate cost, a material/process combination that facilitates industrial-scale production and manufacturing Large parts with relatively thin cross-sections.
  
   Today there are two global GMT suppliers and small specialist producers, often sold in one geographic area. For nearly 30 years, GMT has had little competition in thermoplastics in the composites space, allowing their producers to focus on converting applications previously produced in metal, fiberboard and sheet molding compound (SMC). Therefore, the development of this technology is relatively slow.