Forms of Reinforcement

The available forms of reinforcement follow terminology and technology borrowed from the textile industry. The basic forms described throughout this chapter and other chapters for glass and other fibers including hybrid mixtures are summarized in this chapter. They are continuous filament, woven fabrics, nonwoven fabrics, knitted fabrics, braids, and tapes. 

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Fig. 12. Young s modulus increase in an aluminum composite with SiC reinforcement volume fraction for different forms of reinforcement A, continuous...

Glass fibres are the preferred form of reinforcement for polyester resins since they provide the strongest laminates. Fabrics from other fibres may, however, be used and can in some instances provide adequate reinforcement at lower cost. Glass fibres are available in a number of forms, of which the following are the most important ... 

Glass fibres are the principal form of reinforcement used for plastics because they offer a good combination of strength, stiffness and price. Improved... 

Glass in the form of fibres is relatively inexpensive and is the principal form of reinforcement used in plastics. The fibres are produced by drawing off continuous strands of glass from an orifice in the base of an electrically heated platinum crucible which contains the molten glass. The earliest successful glass reinforcement had a calcium-alumina borosilicate composition developed... 

By far the most common form of reinforcement is fiberglass. Products using unsaturated polyester resin as a matrix and fiberglass fiber reinforcements are commonly referred to as composites , laminates or FRPs (fiber-reinforced plastics). The latter reinforcements are sold as continuous roving, which is continuously chopped in place with a liquid resin stream, chopped roving mat, woven... 

Over the last decade, considerable efforts have been committed to the toughening of sialons and substantial progress has been achieved using various reinforcements. According to the form of reinforcement, sialon composites can be classified as either particle reinforced, discontinuous fibre (whiskers/ short fibres) reinforced, or continuous fibre reinforced. 

Composites can be classified into three groups according to the forms of reinforcement particulate-reinforced, fiber-reinforced, and laminate composites (see Fig. 15.1). A reinforcement is considered to be a particle if all of its dimensions are similar particles can have spherical, platelet, or any regular or irregular geometric form. Particles, usually referred to as fillers, are in some cases added to polymers to reduce costs rather than to reinforce them. Fiber-reinforced composites contain fibers whose lengths are much greater than their cross-sectional dimensions. When the properties vary with... 

Prepregs are used to mold different products. Different forms of reinforcements are used (nonwoven mat, woven fabric, braided, preform, roving, etc.). The TS catalyzed compounded resin is impregnated into the continuous reinforcement and partially cured to a tack-free state in the B-stage (Chapter 3). The impregnated liquid resin provides for precise placement of reinforcement. 

There are several ways in that GMT materials can be manufactured, with various forms of reinforcement providing different properties (Table 4.8 and Figure 4.4). Continuous strand mats impregnated with a TP melt have only limited flow capabilities and cannot be used for deep-draw moldings, products with variations in wall thickness, or with ribs or bosses. Better flow properties are obtained when the sheet is reinforced with needled mats, which are usually produced as part of the main production process. 

Types of reinforcements include fibers of glass, carbon, graphite, boron, nylon, polyethylene, polypropylene, cotton, sisal, asbestos, metals, whiskers, etc. Other types and forms of reinforcements include whiskers, bamboo fibers, burlap fibers, carbon blacks, platelet forms (includes mica, glass, and aluminum), and hemp fibers (Chapter 2). 

Fibre reinforcement. Asbestos fibre reinforced products were extremely popular in the recent past but owing to the inherent health risks its use is now restricted or even prohibited. This restriction has led to much research into alternative forms of reinforcement for thin concrete... 

Two processes for the forming of reinforced thermosets (a) pultrusion and (b) filament winding. 

Although silicon masters are simple to fabricate and offer good resolution and surface properties, they suffer from a number of disadvantages. Silicon masters may be too fragile for typical hot embossing pressures and may need some form of reinforcement (e.g., by anodic... 

Strength. The crystallites consist of many chains aligned closely together and provide some form of reinforcement. The stress is now transferred to the crystals which are made up of lumps of chains. This is the same as if the stress is transferred to hundreds of chains knitted closely together. 

Probably about 90% of all thermoset resins used are polyester resins because they are relatively cheap to make and about three quarters of this production are used with some form of reinforcement. Only the resins with better mechanical and high temperature performance are, however, used with the relatively expensive carbon fibers (Table 13.1). 

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