Ceramic fibres modulus

Reinforcements in the form of continuous fibres, short fibres, whiskers or particles are available commercially. Continuous ceramic fibres are very attractive as reinforcements in high-temperature structural materials. They provide high strength and elastic modulus with high temperature-resistant capability and are free from environmental attack. Ceramic reinforcement materials are divided into oxide and non-oxide categories, listed in Table 3.1. The chemical compositions of some commercially available oxide and non-oxide reinforcements are given in Table 3.2 and Table 3.3. 

Janes, Neumann and Sethna ° reviewed the general subject of solid lubricant composites in polymers and metals. They pointed out that the reduction in mechanical properties with higher concentrations of solid lubricant can be offset by the use of fibre reinforcement. Glass fibre is probably the most commonly used reinforcing fibre, with carbon fibre as a second choice. Metal and ceramic fibres have been used experimentally to reinforce polymers, but have not apparently been used commercially. To some extent powders such as bronze, lead, silica, alumina, titanium oxide or calcium carbonate can be used to improve compressive modulus, hardness and wear rate. 

Various types of fibres could be used in making filter fabrics they include glass fibres, synthehc fibres, ceUulosic fibres (eg, natural wood pulp fibres, viscose fibres, and Lyo-ceU fibres), wool fibres, metal fibres, ceramic fibres, high-performance polymer fibres (eg, inherenfly fire-resistant fibres, chemical resistance fibres, high-strength, and high-modulus fibres), microfibers, and nanofibers. 

Figure 3.3 Modulus for glass, aramid, polyethylene, carbon and ceramic fibres.

This chapter is concerned with continuous ceramic fibres derived from organosilicon polymers, and does not cover precursors to oxide ceramics. It should be noted that effective reinforcement of ceramic matrices can be achieved with whiskers and certain particulate materials, as well as continuous fibres, but these materials are not usually made from polymer precursors and fall outside the scope of this chapter. Apart from reinforcement of ceramics, continuous ceramic fibres have considerable potential for reinforcement of light alloys when enhanced strength and modulus is required at elevated temperature. There is also much interest in the development of plastic matrix... 

It is well known that the Young s modulus of a composite can be calculated by the rule of mixtures for long-fibre reinforced material. In the case of whiskers, the rule of mixture is also applied to estimate the change of modulus (conventionally, reinforcements are added to improve the stiffness of a material, though for ceramic matrix composites this is not always the primary concern). 

Many researchers have used glass and glass-ceramic matrices for reinforcing with high-modulus graphite fibres [1, 2], silicon carbide fibres and silicon carbide mono-filaments [3-7], Very strong, tough and refractory composites were obtained from these efforts. 

The impact of thermal shock on the properties of a ceramic or a CMC is assessed by means of both destructive and non-destructive testing methods. Flexural or tensile (mainly for CMCs) tests of suitably-sized thermally shocked specimens are usually employed to measure retained mechanical properties as a function of the temperature difference. The temperature differential for which a significant drop in property values is observed is the A A- For monolithic ceramics and particle- or whisker-reinforced CMCs the property under investigation is usually strength, whereas in fibre-reinforced CMCs a drop in Young s modulus is usually a better indication of the onset of damage. 

The value of the elastic modulus, often called the Reuss bound, is identical to that for transverse loading on a fibre composite, and gives a value for the elastic modulus normal to the layers. In both of these equations, E, E and Ep are the elastic moduli of the ceramic, matrix and particles, respectively, and Vc (equal to 1.0), Vm and Vp are the corresponding volume fractions. 

In the case of based on poly(vinyl alcohol) soluble fibres, SOLVRON-SX, the sonic solicitation was realised using two ceramic piezoelectric transducers, placed at distance of 12.5 and 17.5 cm, respectively, in different conditions of applied force, P. During solicitation step, the experiments were carried out in standard environmental conditions and both in air and acetone (non solvent of PAV). As Table 3.121 shows the solicitation induced in the relaxation stage the corresponding modification of the ultrasonic rate. The dependence of ultrasonation modulus, and rate, v, with the developed force, P, in the solicitation and relaxation stage, respectively, is illustrated in Figures 350 and 351. 

KasugaT, OtaY., Tsuji K., and Abe Y., "Preparation of High-Strength Calcium Phosphate Ceramics with Low Modulus of Elasticity Containing 3-Ca(POp2 Fibres," /. Am. Ceram. Soc., 79, 1821-24 (1996a). 

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