Pultrusion is a method of manufacturing that refers to a continuous process that utilizes fiber reinforcements and resin matrices to produce constant cross-sectional profiles.

Figure 1. An illustration of the Pultrusion Process
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History
Brandt Goldsworthy, an honored pioneer in the plastics and composites industries, invented the pultrusion process, and he was a major figure in the invention and development of composite material technology.
He came up with the idea of combining various materials together to make stronger plastics while working for an aircraft company that was supplying items for the US Army during the Second World War.
His creations were so successful that he eventually decided to open his own company, where he made several advancements in the field of composites and created certain plastics that were generally stronger than anything previously seen.
Manufacturing Process
Pultrusion refers to a manufacturing process in which continuous lengths of fiberglass reinforced polymers with a constant cross-section are produced.
During this process, reinforced fibers, liquid pultrusion resins, pigments, and other raw materials are normally pulled through a heated die, converting them into FRP composite products.