Metals Polymers Ceramics Composites Classification of Materials

Metals

Polymers Ceramics

Composites

Classification of Materials

Classes of Materials• Metals

– Iron and Steels– Aluminum and Alloys– Copper and Alloys– Nickel and Alloys– Titanium and Alloys

• Ceramics and Glasses– Alumina– Magnesia– Silica– Silicon Carbide– Silicon Nitride– Cement and

Concrete

• Polymers– PE– PMMA– Nylon (PA)– PS– PU– PVC– PET– PEEK– EP– NR

• Composites– GFRP– CFRP

Classes of PropertyEconomic Price and availability

Recyclability

General Physical Density

Mechanical Modulus

Yield and tensile strength

Hardness

Fracture toughness

Fatigue strength

Creep strength

Damping

Thermal Thermal conductivity

Specific heat

Thermal expansion coefficient

Electrical and Magnetic Resistivity

Dielectric constant

Magnetic permeability

Environmental Interaction Oxidation

Corrosion

Wear

Production Ease of Manufacture

Joining

Finishing

Aesthetic Color

Texture

Feel

Metals

• Metals are typically split into ferrous (iron containing) and non-ferrous

• Most widely used metals are alloys except for aluminum and precious metals

• Metals are in general are good thermal and electrical conductors. Many metals are relatively strong and ductile at room temperature, and many maintain good strength even at high temperature.

IronIron was the third of the prehistoric materials ages (stone, bronze, iron). Iron began to be used once furnaces could be made hot enough to melt iron.

Iron quickly became the metal of choice because of its abundance in the earth’s crust.

Iron however has two major problems:

1) Corrosion

2) Brittleness

These problems are partially overcome by alloying iron to make steel

SteelSteel is an alloy consisting mostly of iron, with a carbon content between 0.02% and 1.7 or 2.04% by weight (C:1000–10,8.67Fe), depending on grade. Carbon is the most cost-effective alloying material for iron, but various other alloying elements are used such as manganese and tungsten.[1] Carbon and other elements act as a hardening agent, preventing dislocations in the iron atom crystal lattice from sliding past one another. Varying the amount of alloying elements and form of their presence in the steel (solute elements, precipitated phase) controls qualities such as the hardness, ductility, and tensile strength of the resulting steel. Steel with increased carbon content can be made harder and stronger than iron, but is also more brittle. The maximum solubility of carbon in iron (in austenite region) is 2.14% by weight, occurring at 1149 °C; higher concentrations of carbon or lower temperatures will produce cementite. Alloys with higher carbon content than this are known as cast iron because of their lower melting point.[1]

Steel

Aluminum (Aluminium)• Aluminium or aluminum is a silvery and ductile member of the poor metal group of

chemical elements. It has the symbol Al; its atomic number is 13.• Aluminium is found primarily in bauxite ore and is remarkable for its ability to resist corrosion

(due to the phenomenon of passivation) and its light weight. Structural components made from aluminium and its alloys are vital to the aerospace industry and very important in other areas of transportation and building.

Although aluminium is the most abundant metallic element in Earth's crust (believed to be 7.5% to 8.1%), it is very rare in its free form, occurring in oxygen-deficient environments such as volcanic mud, and it was once considered a precious metal more valuable than gold. Napoleon III, Emperor of France, is reputed to have given a banquet where the most honoured guests were given aluminium utensils, while the other guests had to make do with gold ones.

20th century metallurgists developed improved processes for extraction.

Aluminum

SuperAlloys• A superalloy, or high-performance alloy,

is an alloy able to withstand extreme temperatures that would destroy conventional metals like steel and aluminum. Superalloys exhibit excellent mechanical strength and creep resistance at high temperatures, good surface stability, and corrosion and oxidation resistance. Superalloys typically have an austenitic face-centered cubic crystal structure. A superalloy's base alloying element is usually nickel, cobalt, or nickel-iron. Superalloy development has relied heavily on both chemical and process innovations and has been driven primarily by the aerospace and power industries. Typical applications are in the aerospace industry, eg. for turbine blades for jet engines.

• Examples of superalloys are Hastelloy, Inconel, Haynes alloys, Incoloy, MP98T, TMS alloys, and CMSX single crystal alloys.

Variety of ceramic applications

• Furnace linings, heat sinks, capacitors, fuel cells,

magnets (hard and soft), superconductors,

windows, optical fibers, nuclear fuel, artificial hip

joints, cutting tools, turbine blades, bearings

What is a Ceramic?

• Solid compounds formed by heat or heat and pressure that contain– At least one metal and one non-metal or one

non-metal elemental solid (NMES) [MgO, Al2O3, YBa2Cu3O7]

– At least two NMES [SiC]– At least two NMES and a non-metal

My name is Bond…..

• In ceramics bonding is a mixture of ionic and covalent

• If ionic bonding dominates crystal structures occur that are typically based on FCC and HCP

• If covalent bonding dominates rings and tetrahedral units are often seen

Ceramics: crystalline and glassy

Zinc blende (ZnS) structure

Continuous random network oxide glass

Repeat units of some common polymers

CO COO(CH2)2O n

CH2CH2

n

CHCH2

n

CHCH2

nCH3

• Poly(ethylene)

• Poly(propylene)

• Poly(styrene)

• Poly(ethylene-terephtalate)

Conformation of PolymersAmorphous thermoplastic Semi-crystalline thermoplastic

Crosslinked thermoset

Variety of polymer applications

• Packaging materials, building and

construction, consumer products, electrical

equipment, furniture, adhesives, inks,

coatings, optical films, polarizers,

photoresists, conducting polymers, latex

paint, fabrics/textiles, dielectric materials

(capacitors), light emitting diodes.

PA PE PP UP-GFPBT+PC PVC ABS PPOPBT ABS+PC POM OTHERSPMMA PUR

Plastics use in BMW 5 Series

Elastomers

• Entropy springs

• Lightly crosslinked

• Typically non-linear elastic

(a) (b) (c)

The nitrile groups from neighbouring chains, being polar, attract each other and bind the chains together, making ABS stronger than pure polystyrene. The styrene gives the plastic a shiny, impervious surface. The butadiene, a rubbery substance, provides resilience even at low temperatures. ABS can be used between −25 and

60 °C.Production of 1 kg of ABS requires the equivalent of about 2 kg of oil for raw

materials and energy.

ABS

ABS is used where weight, strength, surface finish and impact resistance are required.

PolycarbonateAlthough polycarbonate has high impact-resistance, it has low scratch-resistance and so a hard coating is applied to polycarbonate eye-wear lenses. The characteristics of polycarbonate are quite like those of polymethyl methacrylate (PMMA; acrylic), but polycarbonate is stronger and more expensive. This polymer is highly transparent to visible light and has better light transmission characteristics than many kinds of glass. CR-39 is a specific polycarbonate material — although it is usually referred to as CR-39 plastic — with good optical and mechanical properties, frequently used for eyeglass lenses.

PC Examples

Polyethylene

Polyethylene is classified into several different categories based mostly on its density and branching. The mechanical properties of PE depend significantly on variables such as the extent and type of branching, the crystal structure, and the molecular weight.Ultra high molecular weight polyethylene (UHMWPE) Ultra low molecular weight polyethylene (ULMWPE - PE-WAX) High molecular weight polyethylene (HMWPE) High density polyethylene (HDPE) High density cross-linked polyethylene (HDXLPE) Cross-linked polyethylene (PEX) Medium density polyethylene (MDPE) Low density polyethylene (LDPE) Linear low density polyethylene (LLDPE) Very low density polyethylene (VLDPE

Polyethylene is one of the most widely used polymers because of its cost and versatility.

Spectra® fiber is one of the world’s strongest and lightest fibers. A bright white polyethylene, it is, pound-for-pound, ten

times stronger than steel, more durable than polyester and has a specific strength that is 40 percent greater than aramid

fiber.    Spectra® fiber is made from ultra-high molecular weight

polyethylene that is used in a patented gel-spinning process. Polyethylene is a remarkably durable plastic, and scientists at Spectra Technologies have captured the tremendous natural strength in the molecular backbone of this everyday plastic to

create one of the world’s strongest and lightest fibers. The gel-spinning process and subsequent drawing steps allow

Spectra® fiber to have a much higher melting temperature (150°C or 300°F) than standard polyethylene.

With outstanding toughness and extraordinary visco-elactic properties, Spectra® fiber can withstand high-load strain-rate

velocities. Light enough to float, it also exhibits high resistance to chemicals, water, and ultraviolet light. It has excellent vibration damping, flex fatigue and internal fiber-friction

characteristics, and Spectra® fiber’s low dielectric constant makes it virtually transparent to radar.

Spectra® fiber is used in numerous high-performance applications, including police and military ballistic-resistant vests, helmets and armored vehicles, as well as sailcloth,

fishing lines, marine cordage, lifting slings, and cut-resistant gloves and apparel. Honeywell also converts Spectra® fiber into the Spectra Shield® family of specialty composites for

armor and other applications.

Polypropylene

Polypropylene is often used as a stronger alternative to polyethylene.

Synthetic Rubber

Based on Butadiene. Cross-linking is needed to create entropy spring.

Composite Materials

Carbon fiber reinforced epoxy crossply laminate

Silicon carbide particulate reinforced aluminum

Silicon carbide monofilament reinforced glass ceramic

After D. Hull and T. W. Clyne, “An introduction to composite materials”, 2nd Edition, Cambridge University Press, Cambridge, (1996)

Polymer matrix composite (PMC)

Metal matrix composite (MMC)

Ceramic matrix composite (CMC)

Review

• Describe the subject of materials science and engineering.

Review

• Cite the primary classifications of solid materials.

Review

• Give distinctive features of each group of materials.

• Metals

• Polymers

• Ceramics

• Composites

Review

• Cite one material from each group.

• Give some applications of different types of materials.