Processing methods pultrusion

Important processing methods injection molding, compression molding, resin transfer molding, pultrusion, casting, encapsulation... 

The mechanical properties of FRP composites are dependent upon the ratio of fibre and matrix material, the mechanical properties of the constituent materials, the fibre orientation in the matrix, and ultimately the processing and methods of fabrication, which are the subject of Part II. Chapters discuss prepreg processing, liquid composite moulding (LCM), filament winding processes and pultrusion of advanced fibre-reinforced polymer (FRP) composites. 

Typical processing methods - BMC, compounding, curing, filament winding, molding, prepreg, pultrusion, RTM, SMC, spraying ... 

Typical processing methods - extrusion, pultrusion, glass mat process ... 

Typical processing methods bulk molding, casting, compression molding, encapsulation, injection molding, printed circuit board, pultrusion, resin transfer molding, sheet molding ... 

Typical processing methods - lay-up, spray-up, filament winding, pultrusion, sheet and bulk molding, vacuum-assisted resin transfer molding ... 

Composite processing uses specialized methods. For thermoplastics, glass mat thermoplastic (GMT) is the main method but prepreg, lay-up, tape winding, pultrusion are also used to produce composites. SMC/BMC are the main processes for thermosets but lay-up is currently used for large parts and prepregs are used for high-tech parts. 

Resin-based composites are usually defined as either conventional or advanced. Conventional composites usually contain glass or mineral fiber reinforcement, and sometimes carbon fiber, either alone or in combination with others. Conventional composites are usually produced in stock shapes such as sheet, rod, and tube. There are many methods of processing composite materials. These include filament winding, layup, cut fiber spraying, resin transfer molding, and pultrusion. 

Initial modelling on predicting velocity profiles in pultrusion dies was carried out by Gorthala et al. (1994). Here a two-dimensional mathematical model in cylindrical co-ordinates with a control-volume-based finite-difference method was developed for resin fiow, cure and heat transfer associated with the pultrusion process. Raper et al. 

Table 9.72 Basic processing (resin transfer, injeetion, pultrusion, and reaetion injection) methods as a function of part design...

If the filaments are not wound onto a mandrel but simply gathered into relatively large bundles and led slowly into a heated consolidation zone, emerging from a die partly or completely cured, the primitive essentials of pultrusion are present (Fig. 2.3(b)). This process began as the thermosetting resin equivalent of extrusion, that is, it was a continuous operation for manufacturing profiles, such as rod and channels. The method has been extended to fibre reinforced thermoplastics. 

Manufacturing methods for composites vary from manual to fully automated processes, whereby the latter have better quality control than the former. Wet layup, pultrusion, and filament winding are all discussed in some detail, while other techniques such as pull-winding, resin transfer moulding, vacuum bag moulding, and injection moulding are left to specialized composite materials texts. 

Practically all resins (TS and TP) are used in RPs, but a few predominate (Tables 7-2 to 7-5), with TS polyesters being the major type. Typical polyesters are summarized in Table 7-4. The polyester RPs are used in all processes, but their principal use is in the low pressure methods (spray-up, hand lay-up, pressure bag molding, casting, pultrusion, rotational molding, filament winding, and compression molding. 

These thermosetting resins contain a urethane prepolymer in methyl methacrylate monomer. Although they are cured in a similar fashion to polyesters, their initial viscosity is much lower and the cure reaction is more rapid. The speed of cure along with the odour of the monomer preclude the use of open mould processes, but these resins are especially suitable for fast processing by methods including pultrusion and resin... 

Clariant has found that use of APP, such as Exolit AP422, and red phosphorus, Exolit RP65x family, in combination with ATH allows useful formulations to be prepared that meet these standards with relatively low loadings of fillers. These can be around 50-70 phr in place of the 150-250 phr for ATH alone. The low viscosity of the resin mixes allows processing by all the conventional methods, such as RTM, hand lay-up, pultrusion etc. 

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. 

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