Mechanical properties - Orthopaedic Biomaterials in Research and Practice - page 56

discussed (see Chapter 2), this is the total area under the stress-
strain curve to ε u and is expressed as an energy per unit volume,
typically with units of J/m 3 .

Material types

It is a usual practice in engineering discussion to generalize the com-
parative values of these parameters and to use overall descriptive terms
for materials. Thus, using the general shape of the stress-strain curves
in Figure 3.2, material A would be called “strong, brittle,” material B ,
“strong, tough,” and material C , “weak, ductile.” We associate type A
curves with ceramics, type B curves with metals, and type C curves with
polymers (and soft tissues). Composite structures (see Chapter 8) have
no single characteristic stress-strain behavior; their utility lies in being
able to combine the mechanical properties of different materials, such
as a ceramic fiber and a polymer matrix, to produce new, intermediate
behavior.

PROBLEM 3.1
In Figure 3.2, which material ( A , B , or C ) is the

Stiffest?
Strongest?
Most ductile?
Most brittle?
Toug h e st?

ANSWER:
A, A, C, A, B.

A

B

σ

C

ε

FIGUre 3.2 typical stress-strain curves.