Material Selection and Production Methods Robert Love, Venkat Jayaraman July 8, 2008 SSTP Seminar – Lecture 5

Overview Topics: Basic Material, Properties, Production Polymers Metals Ceramics Composites Material Selection Discussion Activity 3/25/2017 UF Flight Controls Lab

Polymers - Introduction 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 Polypropylene Metals Polymers The most obvious one is low density for ease of transport and installation, but corrosion resistance is also important for products destined for a long life in a building electrical insulation since non-conducting toughness to resist mechanical abuse such as impact vibration attenuation low weight one shot manufacture Application areas of polymers

Polymers – Properties and Classification 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 Classification based on properties Fiber Elastomer Plastic

Elastomer 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 Uncured natural rubber is sticky and can easily deform when warm, and is brittle when cold. In this state it cannot be used to make articles with a good level of elasticity. The reason for inelastic deformation of unvulcanized rubber can be found in the chemical nature: rubber is made of long polymer chains. These polymer chains can move independently towards each other, and this will result in an irreversible change of shape. By the process of vulcanization crosslinks are formed between the polymer chains, so the chains cannot move independently anymore. As a result, when stress is applied the vulcanized rubber will deform, but upon release of the stress, the rubber article will go back to its original shape.

Plastics 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 The reason for this is that thermoplastics have relatively weak forces of attraction between the chains, which are overcome when the material is heated, unlike thermosets, where the cross-linking of the molecules is by strong chemical bonds. http://www.ides.com/resources/plastic-recycling-codes.asp (Recycle codes)

Mechanical properties comparison Stress Strain Comparison Explain the stress-strain curve on the board

Polymer Production Common-Injection Molding, Thin Films Like the machines in amusement parks that make you a plastic animal… Yep, Lego’s are made of these! 3/25/2017 UF Flight Controls Lab

Metals Examples: Molecular Structure Applications Steel, Aluminum, Magnesium, Gold, Zinc, Silver, Platinum, Alloys, Superalloys Molecular Structure Metallic Bonding: “Sea of electrons” Crystal Lattice Applications Electronics, Structures, Jewelry One of the things I hope you see is how the atomic structure of a material determines it’s bulk properties, which determine it’s applications Great site: http://metals.about.com/cs/properties/l/blproperties.htm 3/25/2017 UF Flight Controls Lab

Properties of Metals Electrical Heat Structural Corrosion 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 Note the connection b/t these properties and their 3/25/2017 UF Flight Controls Lab

Metal Production http://www.rocksandminerals.com/aluminum/process.htm Don’t forget to at least discuss quenching! 3/25/2017 UF Flight Controls Lab

Metal Production Physical Vapor Deposition, Chemical Vapor Deposition, E-Beam Lithography w/Photoresist MEMS/NEMS devices http://www.azom.com/Details.asp?ArticleID=1552 Keep in mind that BULK production is not the only way of making these materials! Use a scanning electron microscope, photoresists etc 3/25/2017 UF Flight Controls Lab

Ceramics Examples Structure Applications 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 Silica (sand), Titanium Carbide-space shuttle, PZT: lead zirconate titanate-a piezoelectric, Ferrite-in magnetic memory-ie your hard drive, Rust (Iron Oxide), Zinc Oxide-semiconductor 3/25/2017 UF Flight Controls Lab

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 Grasp an intuitive feel for how the material behaves by KNOWING it’s atomic structure! 3/25/2017 UF Flight Controls Lab

Ceramic Production Particles->Slurry->Casting, Hand/Kiln (Sintering) 3/25/2017 UF Flight Controls Lab

Composites Examples Structure Applications Concrete, Polymer Matrix + Carbon/Glass/Kevlar fiber Structure Matrix + Reinforcement Combo of 2 of previous 3 material classifications Applications Pressure Chambers, Bikes, Aircraft 3/25/2017 UF Flight Controls Lab

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 Often expensive! 3/25/2017 UF Flight Controls Lab

Composite Production Basic Sequence: By hand: Layup (wet or prepreg) on mold/tool, Vacuum Bag, Bake, Release May have automatic-tape/winding machines 3/25/2017 UF Flight Controls Lab

Material Selection 3/25/2017 UF Flight Controls Lab

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? Have them in groups and deciding on a product (?) Give them a material property comparison chart, give example applications…point to the walls if necessary and ask why they think they made them out of concrete or use paint…etc Hand’s on demo’s: shape memory alloys? Katana? Making a sword: http://www.metacafe.com/watch/178717/sword_making/ How could you characterize a material you’ve never seen before? 3/25/2017 UF Flight Controls Lab

Approximate Temperature Color Approximate Temperature °F °C K Faint Red 930 500 770 Blood Red 1075 580 855 Dark Cherry 1175 635 910 Medium Cherry 1275 690 965 Cherry 1375 745 1020 Bright Cherry 1450 790 1060 Salmon 1550 845 1115 Dark Orange 1630 890 1160 Orange 1725 940 1215 Lemon 1830 1000 1270 Light Yellow 1975 1080 1355 White 2200 1205 1480   3/25/2017 UF Flight Controls Lab