Continuous fiber reinforcement pultrusions

Pultrusion is a modern technique used for producing continuous fiber-reinforced profile in which the orientation of the fiber is kept constant during cure. Although this process is utilized for both thermoplastic and thermoset resins, it is mainly suitable for thermosetting resins like polyester, epoxy and phenolic resin systems. Jute, available in continuous forms such as mat, roving, tapes, yarn, etc., is impregnated with... 

T Asai, T Ohara, T Tanaka, S Hashizume. Method of Manufacturing Continuous Fiber-Reinforced Thermoplastic Prepregs. U.S. Patent 5529652, June 25, 1996. J-M Charrier, PJ Bates, D Guillon, G Zanella. The Effect of Pin Shape on Spreading Roving Filaments for a Thermoplastic Pultrusion Process. 45th Annual Conference, Composites Institute, SPI, Washington DC, 1990, 18-A, pp 1-4. 

Pultrusion. Another method by which thermoplastic fiber-reinforced polymers are produced is pultrusion. In pultrusion, an appropriately designed bundle of continuous fiber strands is drawn through a die along with a molten thermoplastic matrix material. The die serves to consolidate the material combination, and as the matrix material solidifies on exiting the die, a continuous fiber-reinforced structure is produced. Examples of pultruded products include fiberglass rods and reinforced water hoses. 

Extrusion. The process of extrusion is closely related to pultrusion. In extrusion, the plastic material is pushed through a die under pressure rather than drawn through with continuous fiber-reinforcement materials. Random-oriented fiber-reinforcement materials can be used in the extrusion process if they are blended with the molten plastic before entering the die. Extrusion can be used only to produce structures that have a constant cross-sectional profile along their entire length, as determined by the die profile. Quite complex cross-sectional designs can be produced in this way, but they are essentially only two-dimensional. 

Three high volume technologies were used to produce composite parts compression molding, filament winding, and pultrusion. Furthermore, two compression molding techniques were used, one suitable for continuous fiber-reinforced and another for long chopped fiber-reinforced composites (LFTs). 

Recently, new compounding methods have been investigated to produce long, natural fiber-reinforced thermoplastic pellets and improve composite mechanical properties [31, 32]. For example, pellets have been formed by melt impregnation of continuous natural fiber yarns by pultrusion followed by cooling and chopping. Another method involves commingling of continuous forms of natural and synthetic fibers that are then heated, consolidated, and chopped. 

C Koppernses, S Nolet, JP Fanned. Method and Apparatus for Wetting Fiber Reinforcements with Matrix Materials in the Pultrusion Process Using Continuous In-Line Degassing. U.S. Patent No. 5073413, Dec. 17, 1991. 

The impregnated tows can be used for many applications which are generally subdivided into those where the fiber reinforcement is continuous (e.g. filament winding or pultrusion) and those where the tow is cut and the unidirectionally reinforced peUets (discontinuous long fiber reinforced thermoplastics) are then further processed into parts (e.g. in extrusion or injection molding). 

The surface treatment chemistry of glass fiber is normally tailored to match the product function. Reinforcement size chemistries must be compatible with a multitude of processes and with the composite material end-use performance criteria. Processes such as injection molding require chopped fibers with compatibility for thermoplastic compounds. Filament winding and pultrusion require continuous fibers with utihty in thermoset and thermoplastic compovmds. Typically three basic components cue used with glass size chemistries a film former, lubricant, and coupling agent. Readers are directed to the patent literature or [1] and [2] for more specific details. 

Similar to the described combination of pultrusion and extrusion is the so-called pull-extrusion process, which is illustrated in Fig. 8.15. It enables the production of products which are reinforced with both continuous and discontinuous fibers in one profile. A thermoplastic polymer is molten in an extrusion unit. In a first step, the extrudate is combined with a continuous fiber strand. In the second step the remaining polymer is added with... 

Pultrusion is a method for producing continuous lengths of fiber-reinforced parts. A typical pultrusion machine consist of six in-line stations a) filamentar raw material dispensing creels, b) resin impregnation tank, c)excess resin removal devices, d) heated die zone, e) gripping/puUing device, and f) cutoff saw. 

Since pultrusion is an automatic and continuous process for fabricating fiber reinforced plastics, a proper pulling velocity will optimize production rate and mechanical properties. 

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