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engineering materials-Istanbul .technical University | Composite Material | Fiberglass

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C.Ergun Mak214E ã Composites ã None of the single materials can satisfy all demanded properties at the same time. ã But combination for the desired combination of the properties. ã Composite materials: The combination of two or more materials to obtain the desired properties that can not be obtained in the original materials. ã Improved properties: Stiffness, Strength, Hardness, Weight, Corrosion Resistance, Conductivity Mechanical & Physical Properties High Strength: Metals Ceramics High Duct
  1 1 C.ErgunMak214E ã High Strength: MetalsCeramicsã High Ductility MetalsPolymersã High Toughness MetalsPolymersã Good Wear Resistance CeramicsMetalsã Good Corrosion Resistance PolymersCeramicsã Good Electrical Conductivity Metalsã Low Density Polymers ãNone of the single materials can satisfy alldemanded properties at the same time.ãBut combination for the desiredcombinationof the properties.ã Composite materials: Thecombinationof twoormore materialsto obtainthedesired propertiesthat can not be obtained in thesrcinal materials.ã Improved properties :  Stiffness,  Strength,  Hardness,  Weight,  Corrosion Resistance,  Conductivity Mechanical & Physical Properties Composites   2 C.ErgunMak214E Thespecific strengthvs.temperature for several composites and metals.  2 3 C.ErgunMak214E 1.Particulate Compositesa.Dispersion-StrengthenedCompositesb.True ParticulateComposites i.Cemented carbidesii.Abrasivesiii.Electrical Contactsiv.Polymersv.Cast Metal ParticulateComp. 2.Fiber-ReinforcedComposites3.LaminarComposites4.Sandwich Structures Types of Composites   (a)plywood is a laminar composite(b)a fiber-reinforced polymer matrixcomposites(c)concrete;a particulate composite;sand or gravel in a cement matrix 4 C.ErgunMak214E 1.Containsvery hard oxideparticles 10 to 250 nm in diametercalled “dispersoids”in a metal matrix.2.Prevents dislocation motions and provides strengthening.3.No coherencybetweenthedispersoidsandmatrix. 4.No overaging; Goodhightemperaturesporperties.5.No dissolutionin dispersoids orno reactionbetween matrix and dispersoids. 1a.Dispersion-Strengthened Composites Examples:  SAP: SinteredAlpowder up to14% Al 2 O 3 content. Fabricatedwithpowder metallurgy.  TD-Ni( Thoriadispersed Nickel ): First thorium and Nickel powdermixedandpressedto compact the green. Thensinteredinoxygen allowinginternal oxidationof thorium forming thoria.  3 5 C.ErgunMak214E SAP can be useduptoabout 300°C. TD-Ni. The dispersed ThO 2 particles witha diameter of 300nm or less 6 C.ErgunMak214E 1b.True Particulate Composites i) Cemented carbides(Cermets)– Hardceramicparticles bonded with asoftmetallic matrix.ãWCveryhardand toobrittleto be a cutting tool. Co matrix provides goodtoughness.ãProduced withpowder metallurgy: Co andWC powders sintered together.ãOther hard ceramics;TiC, TaC, etc. Microstructure of WC / 20% cobalt-cemented carbide ii) Abrasives: Grinding and cutting wheels.ãHardparticlesbondedbyglassorpolymericmatrix.ãHardparticles;Al 2 O 3 , SiCor BN.  4 7 C.ErgunMak214E The steps in producing a silver-tungsten electrical composite:(a)Press theW powders,(b)a low-densityporouscompactgreen state,(c)Sintering,(d)Infiltrationof liquid silverinto the pores. 1b. True Particulate Composites iii) Electrical Contacts: ãUsedfor electrical contacts inswitchesand relaysãAgoodcombinationof wear resistanceandhighelectrical conductivity.   8 C.ErgunMak214EThe effect of clay on the properties of polyethylene. iv) Polymers: Polymers containingfillers and extenders are particulatecomposites. a)Fillers: Carbon black in vulcanized rubber toimprovestrength, stiffness, hardness, wearandheat resistance. b)Extenders: CaCO 3 , Silica, talc, etc. Forreducing the cost. c)Elastomers: toincreasetoughness. d)Lead (Pb): to use in nuclear application toabsorbradiation. 1b. True Particulate Composites
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