material selection and production methods robert love, venkat jayaraman july 8, 2008 sstp seminar...
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Material Selection and Production Methods
Robert Love, Venkat Jayaraman
July 8, 2008SSTP Seminar – Lecture 5
Overview
• Topics: Basic Material, Properties, Production– Polymers– Metals– Ceramics– Composites
• Material Selection• Discussion• Activity
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• Examples: PET, ABS, PVC, PETE• Polymer – A large molecule of repeating structural
units connected by covalent bonds• Wide variety of applications
• Structural and non structural• Mass-manufactured and one off
Polymers - Introduction
Polypropylene
Application areas of polymers
• Electrical insulation since non-conducting • Toughness to resist mechanical abuse such as impact • Vibration attenuation • Low weight • Ease of manufacture• Ease of transportation and installation
Polymers – Properties and Classification
PlasticFiber Elastomer
Classification based on properties
• Elastomers – Class of polymers which return to their original shape after the applied stress is removed.
• Vulcanization – Curing process of rubber involving high heat and formation of cross links with sulfur
Elastomer
• Thermoplastics – Soften on heating and harden on cooling– Individual strands– Can be remoulded after heating
• Thermosets – – Polymers are crosslinked– Cant melt
• Thermosets are generally harder, more rigid and more brittle, and their mechanical properties are not heat sensitive
Plastics
Mechanical properties comparison
Stress Strain Comparison
Polymer Production
• Common-Injection Molding, Thin Films
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Metals• Examples:
– Steel, Aluminum, Magnesium, Gold, Zinc, Silver, Platinum, Alloys, Superalloys
• Molecular Structure– Metallic Bonding: “Sea of
electrons”– Crystal Lattice
• Applications– Electronics, Structures, Jewelry
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Properties of Metals• Electrical
– High conductivity, low resistivity
• Heat– Excellent conductors, high melting point
• Structural– Heavy, fairly to very strong, ductile/malleable, may be
strengthened by cold work or heat treatment or annealed to reduce strength
• Corrosion– Some highly reactive, some very non-reactive, some
radioactive
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Metal Production
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• Physical Vapor Deposition, Chemical Vapor Deposition, E-Beam Lithography w/Photoresist
Metal Production
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Ceramics• Examples
– Silicon Carbide (SiC), Silica (SiO2), TiC , PZT, Fe3O4, ZnO
• Structure– Ionic or Covalent Bonding– Formed by heat addition– Generally metal+nonmetal
• Applications– High temperature shields, brake pads,
pottery, knives, coatings, electronics
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Properties of Ceramics
• Electronic– Insulators (some exceptions:piezoelectrics PZT),
Semi-conductors, superconductivity
• Heat– Low conductivity, high melting point
• Structural– Heavy, brittle, very strong, low impact resistance
(toughness), stiff, high hardness
• Corrosion– Generally very unreactive, highly scratch resistant
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Ceramic Production
• Particles->Slurry->Casting, Hand/Kiln (Sintering)
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Composites
• Examples– Concrete, Polymer Matrix +
Carbon/Glass/Kevlar fiber
• Structure– Matrix + Reinforcement– Combo of 2 of previous 3
material classifications
• Applications– Pressure Chambers, Bikes,
Aircraft
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Properties of Composites• IT DEPENDS!!!• Electrical
– Usually insulators, some intentionally made conductive
• Heat– Generally heat resistant, depends on matrix
• Structural– Tailor made strength properties (weight reduction), high
stiffness and strength to weight ratio
• Corrosion– May have issues
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Composite Production
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• Basic Sequence: – By hand: Layup (wet or prepreg) on mold/tool,
Vacuum Bag, Bake, Release– May have automatic-tape/winding machines
Material Selection
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Activity
• Think of a need and a product– What material(s) do you need?– What are important properties to consider in the
material selection process?– How will you make this product?
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ColorApproximate Temperature
°F °C K
Faint Red 930 500 770Blood Red 1075 580 855
Dark Cherry 1175 635 910Medium Cherry 1275 690 965
Cherry 1375 745 1020Bright Cherry 1450 790 1060
Salmon 1550 845 1115Dark Orange 1630 890 1160
Orange 1725 940 1215Lemon 1830 1000 1270
Light Yellow 1975 1080 1355White 2200 1205 1480
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