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Polymers and Ceramics Team 6: Christopher Chavez Steve De La Torre David Jaw Matthew Witkowski September 21, 2005 ME260L - PowerPoint PPT Presentation


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Polymers and Ceramics Team 6: Christopher Chavez Steve De La Torre David Jaw Matthew Witkowski September 21, 2005 ME260L Topics: Polymers (S. De La Torre) Additives and Properties (M. Witkowski) Glass and it Properties (D. Jaw)

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Polymers and Ceramics Team 6: Christopher Chavez Steve De La Torre David Jaw Matthew Witkowski September 21, 2005 ME260L

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Polymers and Ceramics

Team 6:

Christopher Chavez

Steve De La Torre

David Jaw

Matthew Witkowski

September 21, 2005

ME260L


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Topics:

  • Polymers (S. De La Torre)

  • Additives and Properties (M. Witkowski)

  • Glass and it Properties (D. Jaw)

  • Properties and Applications of Reinforced Plastic (C. Chavez)

  • References (Team 6)

  • Questions (Team 6)


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Polymers:

  • Things To Know (General Overview)

  • General Information on Polymers (Plastics)

  • Designing with Plastics

  • Did you know? Facts


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Things To Know:

  • Polymers (Plastics);Material capable of being shaped or molded.

  • Synthetic;Manmade polymer

  • Monomer;Basic building block of a polymer, one unit (short molecules)

  • Polymerization;Monomer linked into a repeating unit (long molecules)

  • Amorphous; Short Chain polymers, no crystallinity in solid state

  • Crystallinity;Long chain polymer, dense molecular alignments

  • Glass Temp (Tg);Temp at which a transition occurs (hard vs rubbery)

  • Thermoplastics; Long chains polymers, Plastics that can be repeatedly softened and harded by heating or cooling. E.g. polyethylene, polypropylene

  • Thermosets; Crosslinked polymers,Plastics that can not be softned without degrading the material.


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Polymers (Plastics)

  • What are Plastics?Any one of a large and varied group of materials consisting wholly or part of a combination of carbon and hydrogen (hydrocarbons) e.g. Polyethylene and Polypropylene. Also a combination of oxygen, nitrogen and other organic and inorganic elements. e.g. Polyvinyl Chloride (PVC) and Nylon The invention of new plastics is so rapid that approximately three new plastics are developed each week.

  • Characteristics of Plastics; Plastics are divided into two distinct groups, thermoplastics and thermosets. Chemical resistant (cleaning fluids), thermal and electrical insulators (Cookware handles, thermal underwear). Light weight and varying degrees of strength (toys to space station, pantyhose to Kevlar)

  • Additives; In order to impart certain properties, polymers usually are compounded with additives. Additives modify and improve certain characteristics of the polymer, e.g. stiffness, strength, color, weatherability


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Polymers (Plastics)

  • Producing Plastics; Plastics can be injected molded with great accuracy or machined into components, Extrusion for tube or rod shapes, hot temperature formed, blow molding compressed air blown. In some case, plastics have replaced metal as the material in components for the reason that they are easy to work with and relative inexpensive.

  • Where are Plastics? Whether you are aware of it or not, plastics play an important part in your life. Plastics’ versatility allow it to be used in everything, in fact about nearly every thing we generally use contains plastic. Plastic makes life easier and better. The applications for plastics are almost limitless. e.g. shopping, packaging, home construction.


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Polyethylene

  • Molecular Structure;

  • Common Products; Packaging, Electrical insulation, milk and water bottles, packaging film, house wrap, agricultural film

  • Good gas, chemical and moisture barrier properties, High temperature (high density) allowance, toughness, flexibility, Low melting point (low density).

  • Lower cost than polypropylene


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Polypropylene

  • Molecular Structure;

  • Common Products; Carpet fibers, automotive bumpers, microwave containers,

  • Has excellent chemical resistance, high melting point, flexible to rigid.

  • Low cost and moisture absorption


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Designing with Plastics

  • The number of variations or formulations possible by combining the many chemical elements is virtually endless. This variety also makes the job of selecting the best material for a given application a challenge. The plastics industry provides a dynamic and exciting opportunity.

  • The plastic industry has classified plastics as Durable (3 years or longer of usage e.g. automobiles, electronics, building materials) Non-Durable (3 years or less e.g. trash bags, cups, most toys).

  •   A designer or engineer will often use design equations that work with metals while a part is being designed. Metals behave like a spring; that is, the force generated by the spring is proportional to its length.

  •   When a material actually works this way it is called "LINEAR" behavior. This allows the performance of metals and other materials that work like a spring to be quite accurately calculated. A problem occurs when the designer tries to apply these same equations directly to plastics. Plastics DO NOT BEHAVE LIKE A SPRING (not a straight line), that is they are "non-linear." Temperature changes the behavior even more. The equations should be used only with very special input. A material supplier may have to be consulted for the correct input.


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Designing with Plastics

  • Modulus = Stress/Strain

  • The stress/strain equation is the equation used by designers to predict how a part will distort or change size and shape when loaded. Predicting the stress and strain within an actual part can become very complex. Fortunately, the material suppliers use tests that are easy to understand.

  • The information for all the parameters are supplied by the vendor. The designer need to know what to ask for. Some calculations will still need to be engineered.


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Designing with Plastics

STRESSHow does one know if a material will be strong enough for a part?

If the loads can be predicted and the part shape is known then the designer can estimate the worst load per unit of cross-sectional area within the part. Load per unit area is called "STRESS".

If Force or Load is in pounds and area is in square inches then the units for stress are pounds per square inch


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Designing with Plastics

  • Other parameters to consider when choosing a plastic as your material.

    • Stiffness (Modules); How much is the part going to bend?

    • Strain; How much will the part change under a load to the original shape?

    • Yield Point; When a part is subject to a load, it may no longer return to is original shape.

    • Tensile Strength; Maximum strength of a material with breaking (elongation).

    • Poisson’s Ratio; Material “Necks”

    • Creep; Load and Thermal

    • Shear Strength

    • THE PERFORMANCE OF A PLASTIC PART IS AFFECTED BY: WHAT KIND OF LOAD THE PART WILL SEE (Tensile, Impact, Fatigue, etc.)HOW BIG THE LOAD IS?HOW LONG OR OFTEN THAT LOAD WILL BE APPLIED?HOW HIGH AND/OR LOW A TEMPERATURE THE PART WILL SEE?HOW LONG IT WILL SEE THOSE TEMPERATURES?THE KIND OF ENVIRONMENT THE PART WILL BE USED IN. WILL MOISTURE OR OTHER CHEMICALS BE PRESENT?


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Designing with Plastics

  • THIS IS WHERE PLASTICS DIFFER IN THEIR BEHAVIOR WHEN COMPARED TO OTHER MATERIALS, SUCH AS METALS AND CERAMICS. CHOOSING STRESS AND/OR MODULI VALUES THAT ARE TOO HIGH AND DO NOT ACCOUNT FOR TIME AND TEMPERATURE EFFECTS CAN LEAD TO FAILURE OF THE PART.

  • THIS IS WHERE PLASTICS DIFFER IN THEIR BEHAVIOR WHEN COMPARED TO OTHER MATERIALS, SUCH AS METALS AND CERAMICS. CHOOSING STRESS AND/OR MODULI VALUES THAT ARE TOO HIGH AND DO NOT ACCOUNT FOR TIME AND TEMPERATURE EFFECTS CAN LEAD TO FAILURE OF THE PART.

  • Remember, MATERIALS DON'T FAIL, DESIGNS DO.

  • Link..\..\..\Temp\Assem of 18y-313089&18y-313088.exe


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Did You Know?

  • Between 1990 and 1996 the amount of waste going into landfills declined by more than 17 percent.

  • We are recycling more than ever before. With an average recycling rate of 27 percent, and over 60 percent for some materials, we have exceeded US EPA’s national goal.

  • For every seven trucks needed to deliver paper grocery bags to the store only one truck is needed to carry the same number of plastic grocery bags.

  • Plastic lumber made with recycled plastic, holds nails and screws better than wood, is virtually maintenance free and last for 50 years.

  • Today, 12,000 communities provide recycling service to 184 million people.


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Biodegradable Plastics

Biodegradable- means that microbial species in the environment will degrade a portion (or all) of polymeric material, under the proper environmental conditions, and without producing toxic by-products.

3 Biodegradable Plastics

1. starch-based system: farthest along in production capacity

2. lactic-based system: based in medical and pharmaceutical uses

3. fermentation of sugar: process results in production of a highly crystalline and very stiff polymer (acts similar to polymers from petroleum)


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Crystallinity


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Recycling of Plastics

Recycling Symbols are used to correspond with each plastic:

1. PETE (polyethylene)

2. HDPE (high-density polyethylene)

3. V (vinyl)

4. LDPE (low-density polyethylene)

5. PP (polypropylene)

6. PS (polystyrene)

7. Other


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Elastomers (Rubbers)

Rubber- defined as being capable of recovering from deformations quickly

-Natural rubber: latex base (milk-like sap from inner bark of tropical tree), resistance to fatigue and abrasion

-Synthetic rubbers: better resistance to heat, chemicals, and gasoline than natural rubber.

-Silicones: most useful range of temperature of elastomers, low resistance to oil and wear

-Polyurethane: high strength, as well as harness and stiffness, good resistance to breaking and abrasion


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The Structure of Ceramics

  • Ceramics- compounds of metallic and nonmetallic elements

    • Traditional ceramics: tiles, brick, sewer pipes, and pottery

    • Industrial ceramics (engineering ceramics): used in automotives, aerospace, and turbines

      Raw Materials- clay (oldest, fine-grained sheet-like structure), kaolinite (white clay made of silicate of aluminum, slippery and moldable characteristics), flint (composed of fine silica), feldspar (crystalline minerals with aluminum silicates and potassium, sodium, or calcium)

      Porcelain- white ceramic made of kaoline, quartz, and feldspar


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Types and General Characteristics of Ceramics

Oxide Ceramics

  • Alumina: high hardness and average strength

  • Zirconia: high strength and toughness

    Carbides

  • Tungsten: depend on cobalt binder content

  • Titanium: nickel and molybdenum binder

  • Silicon: high temperature strength and wear tolerance

    Nitrides

  • Cubic boron: 2nd hardest substance (1st diamonds)

  • Titanium: gold in color

  • Silicon: high resistance to thermal and creep

  • Sialon: contains silicon nitrides and other oxides and carbides

    Cermets: made up of oxides, nitrides, and carbides

    Silica: a polymorphic material, high-temperature resistanc

    Nanoceramics and composites

    nanophase ceramics: consist of atomic clusters containing thousands of atoms

    second-phase particles: used as reinforcements in composites (have tensile strength and creep resistance)


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Mechanical Properties

The tensile strength increases with decrease in grain size and porosity

UTS= UTSoe-nPP= volume fraction of pores in the solid

The Modulus of elasticity of ceramics is related to the porosity

E= Eo( 1- 1.9P+ 0.9P2)Eo= the modulus at zero porosity

Ceramics are have less thermal-shock tolerance and impact toughness than metals and thermoplastics. This is due to their lack of ductility. Ceramics have static fatigue caused by cyclic loading. Methods to pre-stress ceramics are:

  • Heat treatment and chemical tempering

  • Laser treatment of surfaces

  • Coating with ceramic of different characteristics

  • Surface-finishing operations


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Physical Properties

Thermal conductivity ranges and is related to porosity

k= ko (1- P)

Thermal cracking- when a small piece or layer breaks off, tends to be lower with a combination of low thermal expansion and high thermal conductivity

Anisotropy of thermal expansion- when thermal expansion ranges with different directions through the ceramic, causes thermal stresses that lead to cracking

Bioceramics- used as biomaterials for human joints because of strength and inertness, they create a structurally strong bond


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Glasses

  • Glass is an amorphous solid with the structure of a liquid.

  • Glass has no distinct melting or freezing point, thus its behavior is similar to that of amorphous alloys and amorphous polymers.


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Is Glass a liquid?

  • Usually when a liquid is cooled to below its melting point, crystals form and it solidifies.

molecular arrangement in a crystal


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Is Glass a solid?

  • If the viscosity rises enough as it is cooled further, it may never crystallize.

  • The molecules then have a disordered arrangement, but sufficient cohesion to maintain some rigidity.

molecular arrangement in a glass


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What is in glass?

  • All glasses contain at least 50% silica, which is known as a glass former.

  • The composition and properties of glasses can be modified greatly by the addition of various other elements.

  • These are known as Intermediates or Modifiers.


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Examples of Glasses

  • Soda Lime Glass

  • General purpose glass

  • Lowest cost


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Examples of Glasses 2

  • Borosilicate Glass

  • Very resistant to chemical attack

  • Easy to cut

  • High luminous transmission

  • Uses are touch control panels, LCD, solar cells


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Examples of Glasses 3

  • Lithium Potash Borosilicate Glass

  • Relatively high operating temperature

  • Microwave window applications

  • Low coefficient of thermal expansion

  • Excellent sealing characteristics


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Glass Ceramics

  • Glass Ceramics have a high Crystalline component to their microstructure.

  • They have a near-zero coefficient of thermal expansion.

  • They are strong because of the absence of the porosity found in conventional ceramics.


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Examples of Glass Ceramics

  • Cookware

  • Heat Exchangers

  • Gas Turbine Engines

  • Housing for Radar Antennas


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Graphite

  • Graphite is a crystalline form of carbon having a sheets of close-packed carbon atoms.

  • Although brittle, graphite has a high electrical conductivity, thermal conductivity, and resistance to high temperature.


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Examples of Graphite

  • Electrodes

  • Heating Elements

  • Furnace parts

  • Pencil lead


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Diamonds

  • A Diamond is a principal form of carbon with a covalent bond structure.

  • It is the hardest substance known.

  • Although brittle, it does resist high temperatures in non-oxidizing environments.


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Uses of Diamonds

  • Jewelry

  • Heat Sinks for Computers

  • Windows for high-power lasers

  • Cutting/Grinding Tools


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Composite Materials

  • A composite material is a combination of two or more chemically distinct materials to form a stronger material.

  • The oldest example of composites, dating back to 4000 BC is the addition of straw to clay in the making of mud huts.


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Examples of Composite Materials

  • Aircraft

  • Space Vehicles

  • Offshore Structures

  • Piping

  • Electronics

  • Automobiles

  • Boats

  • Sporting Goods


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Fiber Reinforced Plastics

  • Fiber Reinforced plastics, also known as polymer-matrix composites, consist of fibers in a polymer matrix.

  • Reinforced plastics have improved fatigue resistance, greater toughness, and higher creep resistance than non-reinforced plastics.


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Examples of FRP

  • Glass Fibers – used most widely, and least expensive of all fibers

  • Graphite Fibers – also known as Carbon Fiber. It is more expensive than Glass Fiber, but also stronger.

  • Boron Fibers – Consists of Boron deposited onto Tungsten. Boron Fibers are very strong, and very resistant to high temperature, but also very heavy and very expensive.


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Properties of Reinforced Plastics

  • The mechanical and physical properties of reinforced plastics depend on the type, shape, and orientation of the reinforcing material.

  • Physical properties of reinforced plastics and their resistance to fatigue, creep and wear depend on type and amount of reinforcement.

  • Critical factor is strength of the bond between fiber and polymer matrix.

    • Weak bonding causes fiber pullout and delamination.


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Effect of Type on Fiber Type on Fiber Reinforced Nylon


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Highest stiffness and strength are achieved when fibers are aligned with tension force.

Unidirectional strongest, weaker transverse properties.

Optimal configuration for specific task.

Weaving techniques for optimal strength


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Applications of Reinforced Plastics

  • First application of reinforced plastic was in 1907 acid resistant tank made of phenolic resin and asbestos fibers.

  • Major development in1970s resulting in advanced composites

  • Fibers used are usually graphite, boron, aluminum oxide, silicon carbide or tungsten

  • Matrix Materials usually consist of aluminum, magnesium, copper, titanium and super alloys.


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  • Typically used in aircrafts, rocket components, automobile bodies, sporting goods and various other structures and components.

  • Boeing 777 is made of 9% composites

    • Weight savings reduced fuel consumption by 2%


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Mercedes-Benz SLR McLaren

  • Carbon fiber body

  • Rigidity and crash performance very good

  • Light weight allows for optimal performance


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Metal-Matrix Composites

  • Advantages of a metal matrix composite (MMC) over a polymer composite are higher elastic modulus, toughness, ductility, and higher resistance to elevated temperatures.

  • Limitations are higher density and greater difficulty in processing parts.

  • MMC Matrix materials are usually aluminum, magnesium, copper, titanium and super alloys.


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Metal-Matrix Composite Materials and Applications


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Ceramic-Matrix Composites

  • Ceramic-Matrix Composites (CMC) are important because of resistance to high temperature and corrosive environments.

  • Ceramics are strong and stiff, resist high temperatures, lack toughness

  • Matrix materials may retain strength up to 1700°C

  • Some CMC matrix materials are silicon carbide, aluminum oxide

  • Some applications of CMC include jet and automotive engine components, structural components and cutting tools.


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Other Composites

  • Composites may also consist of coatings of various metals

  • Plating of aluminum for decorative purposes

  • Enamels

  • Cutting tools and dies, such as cemented carbides and cermets.

  • Precision grinding.


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References

  • http://www.valleydesign.com/pr16.htm

  • http://math.ucr.edu/home/baez/physics/General/Glass/glass.html

  • http://www.dictionary.com

  • Kalpakjin and Shmid. Manufacturing Engineering and Technology. Prentice hall, 5th edition.

  • http://www.nd.edu/~manufact/pdfs/

  • www.germancarfans.com/.../ eng/mercedes/1.html


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