Processing of Composites

The major reinforcing phase is typically continuous glass roving, which is a bundle composed of 1000 or more individual filaments. The most common glass roving used 

In most applications, polyester and vinyl ester resins are used as the matrix materials. Epoxies are also used, although they require longer cure times and do not release easily from the pultrusion dies. Hence, thermosetting resins are most commonly used with pultrusion, although some high-performance thermoplastics such as PEEK and polysulfone can also be accommodated. In addition to the resin, the resin bath may contain a curing agent (initiator, cf. Section 3.3.1.2), colorants, ultraviolet stabilizer, and fire retardant. 

Resin transfer molding (RTM) is a hybrid of two polymer processing techniques we have already described transfer molding and reaction injection molding (RIM). The key difference is that a reinforcement is incorporated during molding to create a composite. 

The reinforcements amenable to RTM are similar to those used for pultrusion, except that they need not be continuous in nature. Thus, E-glass, S-glass, aramid, and carbon fibers are commonly used, as are discontinuous filaments such as wood fiber and polyesters. Even metal and ceramic fibers can be used in this technique. In one method, the preform is fabricated by spraying 12- to 75-mm-long chopped fiber rovings onto a preshaped screen. A binder sprayed with the fibers keeps them in place and holds the preform shape, which is then placed in the mold. 

There are a number of material options available for filament winding. Typical fibers are fiberglass, carbon and aramid. Fiberglass is still the most commonly used 

DMA analysis substantiated the possible morphological features that could partially account for the trend in mechanical and fracture properties of the glass laminate composites [146]. The DMA, done at a frequency of 1 Hz, are given in Fig. 12, where the percentage retention of the room temperature storage modulus (E ) is plotted as a function of temperature to normalize the anomalies resulting from differences in resin content for different systems. EPOBAN-modified 

In the cases of the SPM series of polymers, only a single transition was observed at around 225 °C, which is marginally lower than that of pure BACY. It appears that the two phases are miscible, as otherwise a second transition due to pure BACY should have appeared at higher temperature. The uniform dispersion of the high-Tg polymer and strong matrix/reinfor cement interphase aided 

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Some Features of Processing of Composites with Conducting Fibers. . 138... 

The researches of ZnCFO compatibility with the matrix of isoprene rubber in plasticorder "Brabender" PLE 6511 have shown, that the disperse process of composite is accompanied by lower power consumption and its best compatibility in comparison with zinc oxide (fig. 4). The absence of ZnCFO particles as extraneous impurities in rubber mix also was visually observed, while the zinc oxide particles were well appreciable [7],... 

Library of Congress Cataloging-in-Publication Data Processing of composites / Raju S. Dave, Alfred C. Loos, editors with contributions from F. Abrams... [et al.]. 

During the processing of composite materials in a hot press or an autoclave, the laminate is usually kept flat until cure is complete. If the platen surfaces are assumed frictionless, the effect of the constraints is to require that the curvatures K] and k2 be zero throughout cure. To develop the elastic solution under these constrained conditions, the laminated plate theory may be used with conditions of N = 0 and jc, = 0. The resulting midplane strains are given by... 

The final production process of composite propellant mixing is that of continuous mixing. The continuous mixing system was demonstrated as a production process in 1958. The basic flow sheet for the Polaris... 

This polymer precursor (1) requires relatively inexpensive starting materials, (2) is quite stable in air, (3) offers good processability for polymer infiltration processing of composites, (4) provides excellent SiC ceramic yields and (5) high purity with controllable microstructures. However, one important drawback is the use of costly LiAlHzt. This polymer is now available commercially (Starfire Inc., NY). 

Furthermore, not all applications will need or benefit from the availability of phase pure SiC. For example, in polymer infiltration and pyrolysis processing of composites, the reinforcing material frequently is oxidized at the surface. Thus, an SiC precursor that produces excess carbon may be required to ensure that the oxide surface layer is reduced off during processing so that good interfaces are obtained. 

Liquid-phase infiltration of preforms has emerged as an extremely useful method for the processing of composite materials. This process involves the use of low-viscosity liquids such as sols, metal- or polymer-melts. Using this infiltration process, it is possible to design new materials with unique microstructures (e.g. graded, multiphase, microporous) and unique thermomechanical properties (graded functions, designed residual strains and thermal shock). 

Process a The pellets of neat HDPE and CNTs were mixed in a beaker. Process b Mixed materials was heated. Process c Mixture was mechanically stirred to form dough like suspension. Process d Viscous suspension was compressed to form a plate. Process e Plate was cut into smaller pieces. Process f Processing of composite film... 

The method of processing of compositions HDPE+Z samples in paper [3] was expounded. The initial HDPE and its compositions with contents Z within the interval 0,0H1,0 mass.% were used. The figures in conditional designation of compositions HDPE+Z mean content of Z in mass%. 

Perhaps the most widely exploited cyclic monomer in reactive processing of composite materials via a stepwise reaction is the oxirane or epoxy group (Hodd, 1989). Epoxy resins are principally used to form three-dimensional networks, but linear polymerization is possible. The main linear polyaddition reactions involve catalysed ring-opening in an ionic chain reaction. However, it is appropriate to consider the chemistry of the oxirane group in its reaction with nucleophilic reagents, principally amines, at this point so that the range of possible reactions may be introduced. 

The advantage of optical methods for industrial process control is that they are not subject to electrical interference and have a high bandwidth for information transfer. The theory of fibre-optics and examples of prototype and laboratory-based systems were described earlier in Section 3.4. The use of NIR combined with chemometrics as described in Section 6.10.1 is an example that requires fibre-optics and has the advantage that the components may be made of quartz or even glass and still operate successfully. It is thus possible to treat the optical fibres as disposable items. For example, in autoclave processing of composites, it is possible to leave the fibre embedded in the part and use the optical fibre for subsequent assessment of the condition of the material. 

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