Reinforcement mechanisms cost considerations

Fiber reinforced ceramic matrix composites (CMCs) are under active consideration for large, complex high temperature structural components in aerospace and automotive applications. The Blackglas resin system (a low cost polymer-derived ceramic [PDC] technology) was combined with the Nextel 312 ceramic fiber (with a boron nitride interface layer) to produce a sihcon oxycarbide CMC system that was extensively characterized for mechanical, thermal, and electronic properties and oxidation, creep mpture, and fatigue. A gas turbine tailcone was fabricated and showed excellent performance in a 1500-hour engine test. 

Among the many potential applications of carbon nanotubes (CNTs), their use as reinforcing fillers for fhe fabrication of polymer nanocomposites has received considerable attention [1-4]. Both single-walled and multiwalled carbon nanotubes (SWCNTs and MWCNTs, respectively) are noted for their outstanding thermal, electrical, and mechanical properties. Polypropylene (PP) is a widely used thermoplastic because of its low cost, good processability, and well-balanced physical and mechanical properties. Products of PP take the forms of fibers, films, and molded articles. This chapter highlights the microstructure and properties of PP/CNT nanocomposites. Since most studies dealt with isotactic polypropylene, the term TP" in this chapter refers to isotactic polypropylene unless otherwise stated. 

There is considerable overlap within this category of additives. A particular material, such as glass, may be employed in one application and be considered a reinforcement, but in another application it is called a filler. However, most commonly, a reinforcement is defined as an additive that improves the mechanical properties (e.g., strength) of the polymer system. A filler is defined as an additive that takes up space in the system, generally to reduce cost. A few of the most important additives within this category are described here. 

The advantages of WPC include increased bending strength, stiffness (flexural and tensile modulus), reduced thermal expansion and cost. Mechanical properties such as creep resistance, modulus and strength are usually lower than those of solid wood. WPC are not being nsed in applications that require considerable structural performance [53], although in early 1984, cellulose flour was used to reinforce PA to give PA 12 [54]. 

Conventional concrete structures, and prefabricated steel structures assembled on site and filled with concrete after placement are used in various structures. Precast concrete modules would also be used. Wide use of removable formwork is employed to limit steel exposure to potential corrosion. Prefabrication of reinforced rebar modules is extensively used. In some places mechanical rebar splices are used to reduce the weight of prefabricated modules. All of these techniques have been employed in previous nuclear power plant construction. Steel structures such as the air baffle, and the containment vessel are constructed of steel panels. Panels are made of stiffened steel or corrugated plate depending on availability and cost panels for the baffle are designed with thermal expansion of the containment vessel in mind. Future inspection and maintenance are taken into consideration. 

The structural characteristics of a host polymer material— the matrix—may be improved by including a dispersed material— the reinforcing phase—in various ways. The dispersed phase may be continuous (fiber, tape) or discontinuous (particulate, flake, whisker). We restrict the discussion to reinforcing phases used in fiber (or whisker) form since this article deals with mechanical reinforcement effects rather than with considerations of cost reduction, electrical properties, or... 

In the recent past considerable research and development have been expanded in natural fibers as reinforcement in thermoplastic resin matrix. These reinforced plastics serve as an inexpensive, biodegradable, renewable, and nontoxic alternative to glass or carbon fibers. The various advantages of natural fibers over man-made glass and carbon fibers are low cost, low density, competitive specific mechanical properties, reduced energy consumption and biodegradability. Natural fiber reinforced composites with thermoplastic matrices have successfully proven their qualities in... 

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