Glass Fiber.

FIBER GLASS
Fiberglass   (or fibreglass) (also called glass-reinforced plastic, GRP,[1] glass-fiber reinforced plastic, or GFRP[2]), is a fiber reinforced polymer made of a plastic matrix reinforced by fine fibers of glass. It is also known as GFK.( Glasfaserverstärkter Kunststoff   ).
Fiberglass is a lightweight, extremely strong, and robust material. Although strength properties are somewhat lower than carbon fiber and it is less stiff, the material is typically far less brittle, and the raw materials are much less expensive. Its bulk strength and weight properties are also very favorable when compared to metals, and it can be easily formed using molding processes. The plastic matrix may be epoxy, a thermosetting plastic (most often polyester or vinylester) or thermoplastic.
Common uses of fiberglass include boats, automobiles, baths, hot tubs, water tanks, roofing, pipes, cladding, casts and external door skins.

FIBER:-
Unlike glass fibers used for insulation, for the final structure to be strong, the fiber's surfaces must be almost entirely free of defects, as this permits the fibers to reach gigapascal tensile strengths. If a bulk piece of glass were to be defect free, then it would be equally as strong as glass fibers; however, it's generally impractical to produce bulk material in a defect-free state outside of laboratory conditions.

PRODUCTION:-
The manufacturing process for glass fibers suitable for reinforcement uses large furnaces to gradually melt the silica sand, limestone, kaolin clay, fluorspar, colemanite, dolomite and other minerals to liquid form. Then it is extruded through bushings, which are bundles of very small orifices (typically 5–25 micrometres in diameter for E-Glass, 9 micrometres for S-Glass). These filaments are thensized (coated) with a chemical solution. The individual filaments are now bundled together in large numbers to provide a roving. The diameter of the filaments, as well as the number of filaments in the roving...