Continuous sheets glass reinforcement

Composites. The history of phenoHc resin composites goes back to the early development of phenoHc materials, when wood flour, minerals, and colorants were combined with phenoHc resins to produce mol ding compounds. In later appHcations, resin varnishes were developed for kraft paper and textile fabrics to make decorative and industrial laminates. Although phenoHcs have been well characterized in glass-reinforced composites, new developments continue in this area, such as new systems for Hquid-injection molding (LIM) and sheet-molding compounds (SMC). More compHcated composite systems are based on aramid and graphite fibers. 

Polypropylene sheet has been used most extensively however, thermoplastic polyester, polycarbonate, and nylon versions are available (see Elastomers, synthetic Polycarbonates). Continuous strand glass fiber mat is the typical reinforcement. The limited number of sheet suppHers reduces potential for competitive pricing. 

Glass-mat reinforced thermoplastic (GMT) is similar to SMC and is available in sheet form, reinforced with random oriented fibers that may be continuous or discontinuous. It is manufactured on a double belt press where the glass fiber mats are sandwiched between layers of extruded molten polymer before it enters the press. The thermoplastic is usually about a few millimeters thick and thus stiff, and hence stored as fiat sheets. Another method involves deposition of a molten mixture of resin, chopped fibers, and additives over a moving belt where the water is driven off. The fiber volume fraction in this compound is usually 0.1-0.3 and fiber lengths are in the range of 10-30 mm, unless the reinforcement is continuous. 

Extrusion is the process by which glass-reinforced pellets (alone or in combination with unreinforced pellets) or resin powder and glass are fed into a barrel, heated to plasticity, mixed, and forced to flow in a more or less continuous manner through a forming die which is shaped to produce the required cross section. It is employed to produce sheet, rod, tubes, pipes, and other profiles. 

Glass reinforced fiber in woven, continuous and chopped roving, mat and cloth forms. Can use pre-impregnated sheets of uncured resin and fiber, called SMC. Thermosetting liquid resin commonly catalyzed polyester or epoxy. 

A reinforced plastic sheet is to be made from a matrix with a tensile strength of 60 MN/m and continuous glass fibres with a modulus of 76 GN/m. If the resin ratio by volume is 70% and the modular ratio of the composite is 25, estimate the tensile strength and modulus of the composite. 

Mat and continuous glass fibre reinforcements theoretically all the thermoplastics are usable in these forms, but up to now developments have concentrated on polypropylenes (PP), polyamides (PA) and thermoplastic polyesters (PET) fibre-reinforced PEEK, polyetherimide (PEI) and polyphenylene sulfide (PPS) are used for high-performance applications. They are presented in a range of forms from stampable sheets to pellets, prepregs, ribbons, impregnated or coated continuous fibre rods. More rarely (as in the case of PA 12, for example), the thermoplastic is provided in liquid form. 

GMTs are thermoplastic resin sheets or blanks reinforced with glass mat. Possibly, unidirectional continuous fibres can also be used. 

Thermoforming is another mass production method normally associated with unreinforced or short fibre reinforced thermoplastics, but because of recent developments in reinforced plastics technology, discussed below, there is a greater availability of thermoplastics sheet reinforced by long or continuous glass fibres, so it may become more important for these materials as well. 

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