Reinforced-plastic cutting

Reinforcement. PVA fiber in the form of short cut chips having a length of several millimeters to several tens of millimeters is widely used as raw material for paper and for reinforcing plastics, cement, and the like, and has been acquiring more and more significance. 

Many cellular plastic products are available with different types of protective faces, including composite metal and plastic foils, fiber-reinforced plastic skins, and other coatings. These reduce but do not eliminate the rate of aging. For optimum performance, such membranes must be totally adhered to the foam, and other imperfections such as wrinkles, cuts, holes, and unprotected edges should be avoided because they all contribute to accelerated aging. 

Choosing a reinforced plastic or one from a more-sophisticated polymer family to provide higher performance can be used to cut overall costs by reducing wall thickness and thus reducing material weight and material cost and enhancing the processing. 

Reinforced plastics differ from high-pressure laminates in that little or no pressure is employed. For instance, in making formed shapes, impregnated reinforcing material is cut to a desired shape, the various layers are added to a mold, which is then heated. This process is favored over the high-pressure process because of the use of a simpler, lower cost mold and production of strain-free products. 

A new approach was proposed for making effective helmets which could replace the former British army steel helmet. Essentially the new helmet used modified phenolic resins reinforced with nylon, and the crown cap inside was thermoformed from polyethylene. Formerly the crown cap was attached to the steel by rivets—not an appropriate method for fixing polyethylene to reinforced plastics. Instead a method was developed with a hot-melt adhesive based on ethylene-vinyl acetate copolymers cast as film on release paper. For assembly, the cast film is cut in advance to match the intricate shape required and activated by heat to bond under light pressure subsequently, a further heat activation is employed to fix the crown cap in place (Figure 52 illustrates this). 

Ultrasonic machining (USM) is also of particular importance when very hard type materials are to be cut. As an assist to drilling, HDM energy can extend the drill life when producing holes in reinforced plastics. If the plastic is conductive, electrical discharge machining (EDM) or electrochemical machining (ECM) may be useful. 

Marsh, G., Composite Cutting Considerations, Reinforced Plastics, Nov. 

Reinforced plastics can also be shaped by iryection moulding. Reinforcing material is cut to the shape of the final product and placed in the mould. Metal inserts such as screw threads for bolted portions and other materials required for the product to function are also added at this stage. The mould is closed and the polymer mixed with accelerator is iryected with or without the application of vacuum. 

Fatigue strength of reinforced plastic materials is generally explored with laboratory tests of specimens in cycling machines. Test specimens are specially prepared or cut from the full structure. Such tests, however, cannot provide accurate information about the durability of a complete structure under actual operating conditions. Thus composite structures are sometimes built and subjected to full scale testing. The subject of fatigue is discussed fully in Chapter 5. 

Another example given by Meier et al [21] was related to the reinforcement of the City Hall of Gossau. Here a hole had to be cut in a concrete slab to accommodate an elevator. It was reported that the edges of the hole were strengthened with carbon fibre reinforced plastics sheets instead of thick steel plates. This helps retain the aesthetics of the building and after painting, the presence of carbon fibre reinforced plastic sheets was completely disguised. 

Uses Solvent in hydraulic brake fluids, cutting oils, textile lubricants, printing inks aromatics extraction solvent comonomer in unsat. polyester and alkyd resins reinforced plastics plasticizers in paints cosmetics in food-pkg. adhesives fragrance fixative/diluent petroleum anti-icing additive PU chain extender surfactant for unsat. polyester resins, paints in paper/paperboard in contact with aqTfatty foods defoamer in food-contact coatings in surf, lubricants for mfg. of food-contact metallic articles... 

Cutting of fiber-reinforced plastics Machining of CFRP and composite materials... 

Chang C-S (2006) Turning of glass-fiber reinforced plastics materials with chamfered main cutting edge carbide tools. J Mater Process Technol 180(1-3) 117-129... 

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