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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