Continuous roving

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... 

No. 4 structure in Figure 52 shows another composite structure consisting of unidirectional reinforcement with continuous roving. This structiure was employed by Polymetrics Corp., and NPC, Inc. (25). 

Filament winding of continuous roving for making pressure vessels and pipes has also shown many advances. These advances are concerned with fiber payout and the use of collapsible mandrels for continuous pipe production. 

Property Unit Woven cloth Chopped strand mat Continuous roving... 

Bulked continuous roving can include loops in both the axial and transverse direction... 

Continuous rovings are fed into a cutter and after being cut to the desired lengths, fall into a plenum chamber perforated screen where the air is exhausted from under the screen. A plastic binder of usually up to 5 wt% is applied and is later cured (Figure 5.4). As the glass falls into the plenum chamber, the airflow pattern and baffles inside the screen control its distribution. Preform screen rotates and sometimes tilted to ensure maximizing uniform deposits of the roving. 

Depending on the size and geometry of the part, it is also possible to feed fiber reinforcement in continuous roving form into the mixing head, where it is chopped and mixed with the liquid reacting components and the whole mix is then injected (Figure 5.40). 

Continuous strand Yarn Continuous roving Spun roving Twisted single ends Untwisted multistrands Looped single ends 176,400 yds./lb. to 200 yds./lb 0.0026" diam. to 0.055" diam. 1-2-Vz Filament winding Production of other reinforcements Pultrusion products Preforms... 

Woven roving fabrics Various styles of weave Continuous roving Spun strand roving Staple yard 15 oz to 27 oz./sq. yd. 0.027 to 0.048" thick 2-3-V2 Open mold Laminates Compression molding Bag molding... 

Carbon fibers are also available in continuous roving and as chopped fibers in sizes 1 /8-2 in. 

For electron microscopic investigations, cut and cleaved samples were prepared as described previously from 15x15x100 mm cast concrete-bars containing a continuous roving in the centre [8]. The scanning electron microscopy (SEM) images were recorded on a Hitachi S-3000N. 

Commingled fibre technology involves supplying the matrix in filament form and mingling it with the reinforcing fibres (Fig. 2.4(b)). The two materials can even be cowoven in the same strands. Thus the material is available in the form of continuous roving, chopped fibres, fabrics, etc. Excellent drape qualities can be obtained with fabrics. The technique can be used for pultrusion, but not for filament winding. 

The continuous roving fibre used is cheaper than mat. 

In the spray-up process, a mould is made, just as in the hand-lay-up process. Continuous roving is fed into a chopper gun, which as its name suggests chops the fibres and sprays them onto the mould resin is also sprayed at the same time. The fibre and resin streams meet each other on the mould surface. The laminate is then rolled to remove as much air as possible. The fibre content achieved with this process is typically between 25-35 wt%. This method is rarely used by itself for corrosion-resistant vessels but is used in combination with filament winding for larger vessels. 

The pultrusion process has a low labour requirement and it can manufacture large amounts of profile with high glass-to-resin ratio, using continuous roving at a competitive cost. 

In contrast to extrusion, in pultrusion a combination of liquid resin and continuous fibers is pulled continuously through a heated die of the shape required for continuous profiles. Shapes Include structural I-beams, L-channels, tubes, angles, rods, sheets, and so on, and the resins most commonly used are polyesters with fillers. Other resins such as epoxies and urethanes are used where their properties are needed. Longitudinal fibers are generally continuous rovings. Glass fiber material (mat or woven) is added for cross-ply properties. 

Filament winding. The highest modulus and strength of any plastic material are achieved by filament winding. Continuous roving is pulled continuously through liquid... 

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