Material Families

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No Tutorial in SH-3345 on Jan 22nd

002 SH-3345 Craig Langford [email protected]

003 B&GS-0153 Megan Balsdon [email protected]

004 SEB-2099 Christopher Oreskovic [email protected]

005 SSC-3028 Adam Riese [email protected]

006 B&GS-1056 Benjamin Steen [email protected]

Material Families

ES 1021B

(Text: Chapter 2)

(Try Exercises: E2.9, 10, 13,14 & 18)

The Families of the Material Kingdom

The Families are based on the atomic/molecular structure of the

members

The Hierarchy of the Material Kingdom

Each family has a number of classes, sub-classes and individual

members

Most Elements in the Periodic Table are Metals

Ceramics are Usually Compounds Consisting

of at Least One Non-metal Constituent

Al2O3 , TiC, WC

Family Traits Because the Material Families are based on structure,

and structure determines properties,

We find that Family members have similar properties

Young’s Modulus, E, is how we

characterize the stiffness of a

material.

It is analogous to the ‘spring

constant’ for elastic

deformation.

F

A0

= E ´Dl

l0

E

F

A0

Dl

l0

l0

F

A0

Family Traits

E2.12 Do Zinc alloys have a higher specific stiffness E/p than PP?

Zn:

E/p=100/6

PP:

E/p=1/0.9

Some properties of Metals

1. Metallic solids are made up of atoms that share a “cloud” of valence

electrons (i.e. metallic bonding).

2. This results in very good thermal and electrical conductivity.

3. High elastic stiffness.

4. Pure metals are quite soft and bendable (ductile).

5. Metals can be strengthened by:

- Alloying (mixing atoms of different elements).

- Strain hardening (cold working).

- Heat treating.

6. Usually have high fracture toughness.

7. Almost all metals are crystalline.

8. Metals can be shaped, joined and surface treated in many different

ways.

Non-crystalline metals are called:

-Amorphous metals

-Metallic glass

Some properties of Polymers I

Properties of polymers 1. Long molecules containing a chain of covalent-bonded carbon atoms

2. Molecules joined to each other by weak hydrogen bonds or Van Der Waal bonding.

3. Poor conductors of heat and electricity.

4. Very light weight .

5. Very low elastic stiffness.

6. Not very strong.

7. Very low melting temperature.

8. Very easy to fabricate polymers into complex shapes.

Thermoplastic polymer

(no cross-linking)

Thermoset polymer

(lots of cross-linking)

1. Elastomers are polymers where a very small number of the long

molecules joined together (i.e. cross-linked) by covalent bonds.

2. Able to undergo very large elastic deformation without breaking or

deforming plastically (i.e. elastic bands).

3. Very low stiffness (500 to 5000x lower than metals).

Fig. 4.20 (Text)

Elastomers (few cross-links)

Some properties of Polymers II

Some properties of Ceramics

1. Ceramics are nonmetallic inorganic solids.

2. Compounds made up of two or more elements (i.e. Al2O3, Si3N4, SiC).

3. Ceramics are held together by covalent or ionic bonds.

4. Very low thermal and electrical conductivity.

5. very high stiffness.

6. High strength.

7. Very brittle.

8. Ceramics are crystalline.

9. Very high melting temperature

10. It is difficult to make, shape, join or surface treat ceramic parts because

of their brittleness and their very high melting temperature.

11. Ceramic parts are therefore very expensive.

Some properties of Glasses

1. Glasses are non-crystalline inorganic solids (i.e. non-crystalline ceramics).

2. They are often transparent.

3. Glasses are held together by covalent or ionic bonds (same as ceramics).

4. They therefore have very low thermal and electrical conductivity.

5. They have lower strength, stiffness, and melting temperature than ceramics

because of their lack of uniform atomic spacing.

6. They are usually very brittle (same as ceramics).

7. Low melting temperature

8. It is easier to make parts from glasses than from ceramics because they

melt at a lower temperature.

9. Glass parts are therefore usually less expensive than ceramic parts.

CES Listings of properties of materials and processes are given in reference

books or in computer databases:

Cambridge Engineering Selector (CES)

PC Labs in SEB Rooms 1004, 1012, & 1015.

The CES program can be downloaded to your PC.

Ask the IT help desk.