This chapter examines the following concepts: process overview, reinforcement pre-forming, resin impregnation, die forming and curing, pulling, cutting and trimming, and shapes and applications. Pultrusion is a continuous, high-volume manufacturing process used to make parts of constant cross-section. The name of the process — pultrusion — gives an indication of the basic concept used. In pultrusion, the materials are pulled through the machine wherein they are formed by a die in a manner similar to the extrusion processes used to shape metal and plastics. (Extrusion processes push the material through the die; therein is the fundamental uniqueness of pultrusion.) Continuous fiberglass roving in highcount bundles is the principal reinforcement material for most pultruded parts. Since pultruded parts are continuous, they must be cut for final packaging and shipping. Pultrusion has some major advantages as a composites manufacturing method. The material usage is high because of the ability to make the part to net shape. Also, the throughput rate is high. The process can give high reinforcement content. Hence productivity is the best of all composites manufacturing processes. The disadvantages of pultrusion have limited its use to products in which they are not significant. In pultrusion, the part’s cross-sections must be generally uniform. Therefore, shapes such as tubing, angles, Ibeams, and rods are commonly done. Custom shapes are also possible but they must be of constant cross-section.
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