Ceramic fibers physical properties

With the exception of glass fiber, asbestos (qv), and the specialty metallic and ceramic fibers, textile fibers are a class of soHd organic polymers distinguishable from other polymers by their physical properties and characteristic geometric dimensions (see Glass Refractory fibers). The physical properties of textile fibers, and indeed of all materials, are a reflection of molecular stmcture and intermolecular organization. The abiUty of certain polymers to form fibers can be traced to several stmctural features at different levels of organization rather than to any one particular molecular property. 

Aluminosilicate Fibers. Vitreous alurninosihcate fibers, more commonly known as refractory ceramic fibers (RCF), belong to a class of materials known as synthetic vitreous fibers. Fiber glass and mineral wool are also classified as synthetic vitreous fibers, and together represent 98% of this product group. RCFs were discovered in 1942 (18) but were not used commercially until 1953. Typical chemical and physical properties of these materials are shown in Table 3. 

Table 3. Typical Physical and Chemical Properties of Refractory Ceramic Fibers...

Table 2.6 The chemical compositions, densities, physical and mechanical properties of several commercially available ceramic fibers...

Bone is an anisotropic and viscoelastic ceramic matrix composite and is distinct from conventional ceramics. Its mechanical properties depend on its porosity, degree of mineralization, collagen fiber orientation, and other structural details. The data in Table 18.1 may be used to compare the physical and mechanical properties of bone, hydroxyapatite (the major mineral in bone, and hence, the most relevant material as a bioceramic), and CBPCs. 

Synthetic pol)mieric materials have been widely used in medical disposable supply, prosthetic materials, dental materials, implants, dressings, extracorporeal devices, encapsulants, polymeric drug delivery systems, tissue engineered products, and orthodoses as that of metal and ceramics substituents [Lee, 1989]. The main advantages of the polymeric biomaterials compared to metal or ceramic materials are ease of manufacturability to produce various shapes (latex, film, sheet, fibers, etc.), ease of secondary processability, reasonable cost, and availability with desired mechanical and physical properties. The required properties of polymeric biomaterials are similar to other biomaterials, that is, biocompatibility, sterilizability, adequate mechanical and physical properties, and manufacturability as given in Table 40.1. 

Continuous-length ceramic fibers used to reinforce CMCs must have optimal mechanical, physical, and chemical properties (described in Chapter 2). This chapter reviews the characteristics of fibers that are commercially available and fibers that are at an advanced stage of development. The performance characteristics of interest include stiffness (i.e.. Young s modulus), strength, thermal and electrical conductivity, creep and rupture resistance, oxidation resistance, all as a function of temperature, and strength and stiffness retention as a fimetion of serviee history. The critical issue of chemical compatibility with prospective interface coatings and the eeramie matrix is addressed in Chapter 4 and Chapter 6. 

In the last few decades, polymeric materials have found many applications and govern a major part of our day-to-day life. The polymeric materials are strong, lightweight, and easily processable with cost-effective techniques [1]. However, the properties of the pure polymeric materials limit their application in diversified fields. The introduction of filler materials into the polymer matrix generates properties superior to those of individual components. The combination forms a single system the polymer nanocomposites exhibit improved strength, stiffness and dimensional stability with adequate physical properties compared to pure ploymer. These nanocomposites can be of different types such as ceramic-based nanocomposites, fiber-reinforced nanocomposites, polymer-clay nanocomposites, etc. 

One example of a recently introduced ceramic fiUer/reinforcement is short discontinuous fibers composed of approximately equal parts of alumina and silica. This filler has a melting temperature of 1795°C. It can be engineered for a specific set of physical properties by modifying fiber length, diameter, aspect ratio, and surface area. 

The common commercially available fibers used in composites are fiberglass, graphite (carbon), aramid, polyethylene, boron, silicon carbide, and other ceramics such as silicon nitride, alumina, and alumina silica. Many matrix choices are available, both thermosetting and thermoplastic. Each type has an impact on the processing technique, physical properties, and environmental resistance of the finished composite. The most common resin matrices include polyester, vinyl esters, epoxy, bismaleimides, polyimides, cyanate ester, and triazine. 

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