Glass-fiber reinforced plastics, compression

GE Plastics markets a range of composites (Azloy ) based on glass hber reinforced PC, PC/PBT (Xenoy ) or PPE alloys. The glass fiber reinforcement is in the form of mats or chopped fibers. Parts with these materials are formed by compression molding. The materials are commercially available in the form of precompounded sheets from which blanks are cut and stamped into the final shape following the standard rules for glass filled materials. For example, better flow is obtained with the reinforcement in the form of chopped fibers than with mats. The type of reinforcement determines the ability to hll complex parts, such as parts with ribs. 

Chrysler specified a modified polymethyl methacrylate (PMMA) laminating resin for the body panels of the high-performance sports car, the 400 bhp 10 cylinder Dodge Viper, which went on sale in January 1992. The transition from styling to production took only three years. The decision to use glass fiber reinforced PMMA resin, molded by resin transfer, was a fundamental departure from established Chrysler practice, where previously all main exterior bodywork had been in sheet metal. However, at expected sales of 3000 a year and a unit price of about 50,000, sheet metal would not have been viable and the annual volume was too low to justify injection or compression molded plastics. 

The resin matrix can be either thermosetting or thermoplastic. Thermosetting resins such as epoxy, polyimide, polyester, and phenolic are used in applications where physical properties are important. Polyester and epoxy composites make up the bulk of the thermoset composite market. Of these two, polyesters dominate by far. Reinforced with glass fiber, these are known as fiberglass-reinforced plastics (FRPs). FRPs are molded by layup and spray-up methods or by compression molding either a preform or sheet molding compound (SMC). 

In use are stamping compression molding presses. Plastic used can be TS sheet molding compounds (SMCs) and stampable reinforced thermoplastic sheet (STX) material (STX is a registered tradename Azdel Inc., Shelby, NC). It is usually composed of a glass fiber-thermoplastic RTP (Chapter 15). 

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