The initial liquid or solid phase peritectoid

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Unformatted text preview: train hardening ferrite and cementite temperature. Thus, matrix some steels. contributes significantly to the strength of the composite. Pearlite forms by the decomposition of austenite. percent reduction in area The change in area 14.4 PRACTICAL COMPOSITE SYSTEMS (%RA) divided by the original area (expressed in percent) of a So far composites have been classified as unidirectional fiber composites, continuous and discontinuous fiber composites, laminates,has been three-dimensional woven-fabric tensile specimen that two- and fractured. composites, particle-reinforced composites, and so on. These classifications are based peritectic reaction The transformation, during cooling, on the architecture and characteristics of the reinforcing phase. Composites are also of a by their matrix types, including metal-matrix, polymer-matrix, frequently classified solid and a liquid phase isothermally and reversibly ceramic-matrix, and carbon-carbon composites. Some important commercial composites into a solid having a different composition from either in each of these classes are described below. the initial liquid or solid phase. peritectoid reaction The transformation, during 14.4.1 Metal-Matrix Composites cooling, of two solid phases plasma spray of and reversibly Metal-matrix composites (MMCs) are fabricated by isothermally the matrix material over properly laid fibers, liquidhaving a different composition from hot pressinto a solid infiltration methods, physical vapor deposition, either of ing, squeeze casting, and other methods. These methods are discussed in Chapter 16. the initial solids. MMCs have good high-temperature capability, good transverse properties, and reasonably high compressive and shear strength, inmolecule inof a combination of good permanent dipole A part because which the spatial strength and toughness of the metal matrix and good interface bonding. Common MMC center of positive charge is always different from that of systems include boron fibers in an aluminum matrix, SiC fibers or whiskers in an aluminum matrix,the negative charge. and carbon fibers in magnesium, copper, or SiC in a titanium matrix, aluminum matrices. Applications include piston heads for automotive engines, relates the permeability The materials property that connecting rods in engine crankshafts, gas turbine blades, radar domes, and electronic packages. magnetic MMCs are B, in Table 14.4–1. Typical properties of some inductiongivento the magnetic field strength H. permittivity See dielectric constant. 14.4.2 Polymer-Matrix Composites Petch-Hall equation Equation that provides the Polymer-matrix composites (PMCs) are the workhorse of the and the yield stress. relationship between the grain size composites industry. They can have excellent room-temperature properties at a comparatively low cost. They have been in use for The yield stressTwo of the best known early uses in the 1950s are in about four decades. increases with decreasing grain size body panels for the Chevy Corvette Petch-Hall equation. The matrix cons...
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This note was uploaded on 02/25/2013 for the course PHYS 2202 taught by Professor Sowell during the Spring '10 term at Georgia Institute of Technology.

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