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Composites Groover

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groover kitabından composites özeti
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  02.01.20141 COMPOSİTES Groover  ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing  3/e Composite Material Defined A materials system composed of two or more distinct phases whose combination produces aggregate properties that are different from those of its constituents  Examples:  Cemented carbides (WC with Co binder)  Plastic molding compounds with fillers  Rubber mixed with carbon black  Wood (a natural composite as distinguished from a synthesized composite)  02.01.20142 ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing  3/e Our Classification of Composite Materials 1.Metal Matrix Composites (MMCs) -mixtures of ceramics and metals, such as cemented carbides and other cermets 2.Ceramic Matrix Composites (CMCs) -Al 2 O 3 and SiC imbedded with fibers to improve properties3.Polymer Matrix Composites (PMCs) -polymer resins imbedded with filler or reinforcing agent  Examples: epoxy and polyester with fiber reinforcement, and phenolic with powders ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing  3/e Functions of the Matrix Material  Primary phase provides the bulk form of the part or product made of the composite material  Holds the imbedded phase in place, usually enclosing and often concealing it  When a load is applied, the matrix shares the load with the secondary phase, in some cases deforming so that the stress is essentially born by the reinforcing agent  02.01.20143 ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing  3/e The Reinforcing Phase  Function is to reinforce the primary phase  Imbedded phase is most commonly one of the following shapes:  Fibers  Particles  Flakes  Also, secondary phase can take the form of an infiltrated phase in a skeletal or porous matrix  Example: a powder metallurgy part infiltrated with polymer  ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing  3/e Physical Shapes of Imbedded Phase Figure 9.1 Possible physical shapes of imbedded phases in composite materials: (a) fiber, (b) particle, and (c) flake.  02.01.20144 ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing  3/e Fibers Filaments of reinforcing material, usually circular in cross-section  Diameters from less than 0.0025 mm to about 0.13 mm, depending on material  Filaments provide greatest opportunity for strength enhancement of composites  Filament form of most materials is significantly stronger than the bulk form  As diameter is reduced, the material becomes oriented in the fiber axis direction and probability of defects in the structure decreases significantly ©2007 John Wiley & Sons, Inc. M P Groover, Fundamentals of Modern Manufacturing  3/e Continuous vs. Discontinuous Fibers  Continuous fibers -very long; in theory, they offer a continuous path by which a load can be carried by the composite part  Discontinuous fibers (chopped sections of continuous fibers) -short lengths (L/D = roughly 100)   Whiskers = discontinuous fibers of hair-like single crystals with diameters down to about 0.001 mm (0.00004 in.) and very high strength
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