Fibreglass (US: fiberglass), often called glass-reinforced plastic (GRP), is a type of composite material consisting of glass-based fibres embedded in a polymer matrix. In this combination the continuous or chopped fine fibres supply tensile strength while the surrounding plastic binds the structure, transfers loads, and protects the fibres from abrasion and moisture. The glass element itself is ordinary glass drawn into filaments; common fibre formulations are engineered for strength, electrical insulation, or chemical resistance.

Structure and primary properties

Fibreglass achieves a favourable strength-to-weight ratio because glass fibres carry most of the load while the polymer controls shape and toughness. The matrix is usually a thermoset such as epoxy or polyester resin, though modern composites can use a thermoplastic matrix for recyclability and faster processing. Mechanical performance depends on fibre type, orientation and volume fraction; lay-up and curing determine stiffness, impact resistance and fatigue life. Advantages include corrosion resistance, electrical insulation, and the ability to be moulded into complex geometries.

Origins and development

Glass-reinforced plastics were developed in the early 20th century as glass-fiber production and polymer chemistry advanced. Commercial use expanded after the 1930s and accelerated in the post–World War II era when manufacturers adopted GRP for boats, vehicles and industrial parts. Over decades, manufacturing techniques and resin formulations improved, giving the material wider industrial and consumer applications.

Common uses and examples

  • Marine hulls and superstructures: durable, rot-resistant boat construction.
  • Automotive and transportation: body panels, interior parts and light structural components.
  • Industrial equipment: tanks, pipes and corrosion-resistant housings.
  • Sporting goods and consumer items: windsurf boards, helmets, and fixtures where light weight and shapeability are important.
  • Renewable energy: blades and housings for wind turbines where long, slender moulded parts are needed.

Advantages, limitations and notable distinctions

Fibreglass is generally less costly and more flexible than carbon fibre, and it is often stronger than many metals when compared on a weight basis. It resists many corrosive environments and is electrically insulating. Limitations include lower stiffness than carbon fibre, potential degradation of some resins under UV exposure, and difficulties in recycling thermoset-based products. Manufacturing choices — hand lay-up, spray-up, resin transfer molding or filament winding — influence cost, repeatability and part performance.

Because properties vary with fibre type (for example, different glass grades) and resin chemistry, designers select GRP formulations to balance cost, strength, durability and manufacturability. For further technical background and materials data, see specialized resources and standards guides provided by industry and materials suppliers (composite overview, epoxy systems, polyester systems).