Plastics continuous fiber reinforcements

Domier has developed a production route for continuous fiber-reinforced ceramics based on the impregnation and pyrolysis of Si-polymers. This process is related to the manufacturing of fiber-reinforced plastics and allows the cost-effective production of large and complex CMC-structures. 

Continuous-fiber reinforcement gives plastic products which are not simply quantitatively, but often qualitatively, superior to most present commercial practice. Most plastic processing is limited to conventional melt flow of short-fiber reinforcements, which sacrifices much of the potential benefits of reinforcement. There are a few processes for incorporating continuous fiber reinforcement—filament-winding, pultru-sion, swirl conformation of fibers in polymer... 

Consider a continuous fiber-reinforced ceramic as a multiphase system where the individual phases are parallel to one another and to the uniaxial loading direction. The fibers (or fiber bundles), matrix, and interface zone are treated as individual phases. In general, each phase undergoes elastic-plastic (creep) deformation. In the present analysis, the creep rate of each phase, e is assumed to obey a general creep law of the following form... 

Fig. 6 Processes of environment-conscious material design of precast lightweiht concrete reinforced with continuous fiber reinforced plastic (FRP) reinforcement...

From the viewpoint of the easiness of demolition and recycling, not ordinary steel reinforced concrete (RC) cast-in place completely in a body, but hybrid structural systems composed of steel reinforced precast RC columns and new continuous fiber reinforced plastics (FRP) reinforced lightweight precast concrete (FRPRC) beams connected with steel fasteners are recommended. 

In flexure or shear, as in the previous case of compression, plastics reinforced with short fibers are probably better than those with continuous fibers, because in the former with random orientation of fibers at least some of the fibers will be correctly aligned to resist the shear deformation. However, with continuous-fiber reinforcement if the shear stresses are on planes perpendicular to the continuous fibers, then the fibers will offer resistance to shear deformation. Since high volume fraction (f>() can be achieved with continuous fibers, this resistance can be substantial. 

Polymeric materials have relatively large thermal expansion. However, by incorporating fillers of low a in typical plastics, it is possible to produce a composite having a value of a only one-fifth of the unfilled plastics. Recently the thermal expansivity of a number of in situ composites of polymer liquid crystals and engineering plastics has been studied [14,16, 98, 99]. Choy et al [99] have attempted to correlate the thermal expansivity of a blend with those of its constituents using the Schapery equation for continuous fiber reinforced composites [100] as the PLC fibrils in blends studied are essentially continuous at the draw ratio of 2 = 15. Other authors [14,99] observed that the Takayanagi model [101] explains the thermal expansion. 

Table 7.2 Comparative properties of continuous fiber reinforcements for plastics [8].

Extrusion. The process of extrusion is closely related to pultrusion. In extrusion, the plastic material is pushed through a die under pressure rather than drawn through with continuous fiber-reinforcement materials. Random-oriented fiber-reinforcement materials can be used in the extrusion process if they are blended with the molten plastic before entering the die. Extrusion can be used only to produce structures that have a constant cross-sectional profile along their entire length, as determined by the die profile. Quite complex cross-sectional designs can be produced in this way, but they are essentially only two-dimensional. 

To fabricate continuous fiber-reinforced plastics that meet design specifications, the fibers should be uniformly distributed within the plastic matrix and, in most instances, all oriented in virtually the same direction. This section discusses several techniques (pul-trusion, filament winding, and prepreg production processes) by which useful products of these materials are manufactured. 

Figure PI2.14 Unidirectional continuous-fiber reinforcement of plastics...

The term reinforced plastic (RP), also called composites (more accurately plastic composites), refers to combinations of plastic (matrix) and reinforcing materials that predominantly come in fiber forms such as chopped, continuous, woven and nonwoven fabrics, etc. also in other forms such as powder, flake, etc. They provide significant oriented property and/or cost improvements than the individual components (10, 14, 35, 38, 39-43, 62). 

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... 

The second main ingredient in reinforced plastic is the reinforcement, eg, fibers of glass, carbon, boron, mineral, cellulose, or polymers. Reinforcements can be configured in many ways, such as continuous or chopped strands, milled fibers, rovings, tows, mats, braids, and woven fabrics. 

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