Polymeric fiber-reinforced composites

The performance characteristics of a composite material depend on the type of reinforcing fiber (its strength and stiffness), its length, fiber volume fraction in the matrix, and the strength of the fiber-matrix interface. The presence of voids and the nature of the matrix are additional but minor factors. 

The majority of commercially available polymeric composites are reinforced by glass fibers, carbon fibers, aramid fibers (e.g., Kevlar) and, to a lesser degree, boron fibers. In some cases hybrid composites are made that contain combinations of fibers. 

Matrix materials for commercial composites are mainly liquid thermosetting resins such as polyesters, vinyl esters, epoxy resins, and bismaleimide resins. Thermoplastic composites are made from polyamides, polyether ether ketone (PEEK), polyphenylene sulfide (PPS), polysulfone, polyetherim-ide (PEI), and polyamide-imide (PAI). 

Thermosetting composites are cured at either ambient or elevated temperatures to obtain a hard solid by cross-linking. The use of radiation cross-linking decreases the cure time considerably. In particular, an electron beam has been used successfully in many instances. Eor example, glass-fiber-reinforced composites cured by electron beam have been used for the production of cladding panels.  

The production of materials having good mechanical properties matching those produced by conventional thermal methods has been achieved by 

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Liquid Composite Molding (LCM) is the common name for several similar processes for the manufacturing of polymeric fiber reinforced composites. Widely used processes that belong to this class are Resin Transfer Molding (RTM), Vacuum-Assisted Resin Injection (VARI), and Structural-Reaction Injection Molding (S-RIM). 

The main potential for expansion of UV/EB into aerospace and certain commercial applications is by developing radiation curing of polymeric fiber-reinforced composites. The initial work on composite skin repairs involve applying the UV curing technology with bisacryl phosphine oxide to ensure the cure of relatively thick layers. A total of ten layers were used at a time. The UV cured composites closely matched those produced by heating. ... 

Laminating Adhesives Polymeric Fiber-Reinforced Composites... 

Among the more common thermoplastics from ring opening polymerization of interest in composite processing are polylactams, polyethers, polyacetals, and polycycloolefins. It has also been shown that polycarbonates can be produced from cyclic carbonates [22], Anionic ring opening polymerization of caprolactam to nylon 6 is uniquely suited to form a thermoplastic matrix for fiber-reinforced composites, specifically by the reaction injection pultrusion process [23-25]. The fast reaction kinetics with no by-products and the crystalline... 

Plastics are by far the largest group of polymeric materials being processed by electron beam irradiation. Cross-linking of polyolefins, PVC, polyesters, polyurethanes, fluoropolymers, and fiber-reinforced composites is a common practice. 

MIC of Materials. Many cases have been documented of the biodeterioration by bacteria and/or fungi of architectural building materials, stonework, fiber-reinforced composites, polymeric coatings, and concrete.66 Biodeterioration then proceeds by the processes of staining, patina formation, pitting, etching, disaggregation, and exfoliation. (Dexter)5... 

In this chapter, we define some important terms and parameters that are commonly used with fibers and fiber products such as yams, fabrics, etc., and then describe some general features of fibers and their products. These definitions, parameters, and features serve to characterize a variety of fibers and products made from them, excluding items such as fiber reinforced composites. These definitions and features are generally independent of fiber type, i.e. polymeric, metallic, glass or ceramic fibers. They depend on the geometry rather than any material characteristics. 

Another effect of the high degree of chain alignment in these fibers is manifested when they are put in a polymeric matrix to form a fiber reinforced composite. High modulus polyethylene fibers such as Spectra or Dyneema are hard... 

Among the main disadvantages of using polymers as structural components in engineering are their low stiffness and strength. To improve these properties, reinforced polymers or polymeric matrix composites are prepared. Chapter 15 provides an overview of these materials, mainly fiber-reinforced composites since they exhibit the best mechanical properties. 

Closed-form expressions from composite theory are also useful in correlating and predicting the transport properties (dielectric constant, electrical conductivity, magnetic susceptibility, thermal conductivity, gas diffusivity and gas permeability) of multiphase materials. The models lor these properties often utilize mathematical treatments [54,55] which are similar to those used for the thermoelastic properties, once the appropriate mathematical analogies [56,57] are made. Such analogies and the resulting composite models have been pursued quite extensively for both particulate-reinforced and fiber-reinforced composites where the filler phase consists of discrete entities dispersed within a continuous polymeric matrix. 

If the materials are anisotropic, they will present different properties in the different directions. Examples of these polymeric materials are polymer fibers, such as polyethylene terephthalate, PET, nylon fibers, injection-molded polymers, fiber-reinforced composites with a polymeric matrix, and crystalline polymers where the crystalline phase is not randomly oriented. A typical method for measuring the modulus in tension is the stress-strain test, in which the modulus corresponds to the initial slope of the stress-strain curve. Figure 21.4 shows typical stress-strain curves for different types of polymeric materials. 

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. 

In situ polymerization to prepare immiscible blends was pioneered by Watkins and McCarthy [108], stimulating other researchers to apply this methodology to prepare novel polymer blends [109-112], fiber-reinforced composite materials[39], and electrically conducting composites [66, 67, 113-116]. Polymer blends produced in this manner include polystyrene/poly(vinyl chloride) [117, 118], polysty-rene/PET [119], nanometer-dispersed polypropylene/polystyrene interpenetrating networks [120], polypropylene/polystyrene [121] and polyethylene/polystyrene [122]. The resultant polymer blend may have a unique morphology compared to the traditionally prepared counterpart (if it is feasible to prepare such a blend via conventional procedures) and therefore demands a thorough investigation. 

Acoustic emission has been frequently used in studies of the fracture behavior of fiber-reinforced composites. This method was also adopted to studies of blends. Since the sound is most frequently generated by debonding of two phases, there should be a drastic difference in the acoustic activity for blends located on the two sides of spinodal. To quantify miscibility between PVC and EVAc, acoustic emission measurements during a peel test of a-PVC/EVAc/PVC sandwich were carried out (Muniz et al. 1992). The authors considered that the acoustic emissions at slow rates of peeling are related not to the viscoelastic dissipation processes, but rather to the work necessary to puU apart polymeric chains or break bonds. The highest acoustic emission was obtained for VAc content in EVAc of 18 and 29 wt%. 

Different kinds of biobased polymeric materials are available all around the globe. These biobased materials are procured from different biorenewable resources. Chapters 2-10 primarily focus on the use of different types of lignocellulosic fiber-reinforced composites, starting from wood fibers to hybrid fiber-reinforced polymer composites. Chapter 3 summarizes some of the recent research on different lignocellulosic fiber-reinforced polymer composites in the Southeast region of the world, while Chapter 6 summarizes the research on some typical Brazilian lignocellulosic fiber composites. The polymers obtained from biopolymers are frequently referred to as biobased... 

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