Fundamentals of Materials Science and Engineering: An Integrated Approach, 3e

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1.4 Classification of Materials • 7

Strength (Tensile Strength, in units of

megapascals) (logarithmic scale)

1000

100

10

Nylon

PS

PE

PVC

PTFE

Polymers

Steel

alloys

Gold

Aluminum

alloys

Cu,Ti

alloys

Metals

CFRC

GFRC

Composites

Glass Woods

Si 3 N 4

SiC

Ceramics

Al 2 O 3

Figure 1.5

Bar-chart of

room-temperature

strength (i.e., tensile

strength) values for

various metals,

ceramics, polymers,

and composite

materials.

Ceramics

Ceramics are compounds between metallic and nonmetallic elements; they are most

frequently oxides, nitrides, and carbides. For example, some of the common ceramic

materials include aluminum oxide (oralumina,Al 2 O 3 ), silicon dioxide (orsilica,

SiO 2 ), silicon carbide (SiC), silicon nitride (Si 3 N 4 ), and, in addition, what some refer

to as thetraditional ceramics—those composed of clay minerals (i.e., porcelain), as

well as cement and glass. With regard to mechanical behavior, ceramic materials

are relatively stiff and strong—stiffnesses and strengths are comparable to those of

the metals (Figures 1.4 and 1.5). In addition, ceramics are typically very hard. On

the other hand, they are extremely brittle (lack ductility) and are highly susceptible

Resistance to Fracture (Fracture Toughness,

in units of MPa m) (logarithmic scale)

100

10

1.0

0.1

Composites

CFRC GFRC

Woods

Nylon

Polymers

Polystyrene

Polyethylene

Polyester

Al 2 O 3

SiC

Si 3 N 4

Glass

Concrete

Ceramics

Metals

Steel

alloys

Titanium

alloys

Aluminum

alloys

Figure 1.6 Bar-chart of room-temperature resistance to fracture (i.e., fracture toughness)

for various metals, ceramics, polymers, and composite materials. (Reprinted from

Engineering Materials 1: An Introduction to Properties, Applications and Design,third

edition, M. F. Ashby and D. R. H. Jones, pages 177 and 178, 2005, with permission from

Elsevier.)