Chapter
Introduction to Materials
1
Science and Engineering
Have You Ever Wondered?
●● What do materials scientists and engineers study?
●● From a materials stand point, how do you significantly improve the fuel
efficiency of a commercial jet airliner?
●● Can we make flexible and lightweight electronic circuits using plastics?
●● Why do jewelers add copper to gold?
●● What is a “smart material?”
Chapter Learning Objectives
The key objectives of this chapter are to
●● Understand the primary concepts that define materials science and engineering.
●● Understand the role of materials science in the design process.
●● Classify materials by properties.
●● Classify materials by function.
I
n this chapter, we will first introduce you to the field of materials science and
engineering using different real-world examples. We will then provide an intro-
duction to the classification of materials. Although most engineering programs
require students to take a materials science course, you should approach your study
of materials science as more than a mere requirement. A thorough knowledge of
materials science and engineering will make you a better engineer and designer.
Materials science underlies all technological advances, and an understanding of the
basics of materials and their applications will not only make you a better engineer,
but will help you during the design process. In order to be a good designer, you must
learn what materials will be appropriate to use in different applications. You need to
be capable of choosing the right material for your application based on its properties,
and you must recognize how and why these properties might change over time and
due to processing. Any engineer can look up materials properties in a book or search
databases for a material that meets design specifications, but the ability to innovate
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4 Chapter 1 Introduction to Materials Science and Engineering
and to incorporate materials safely in a design is rooted in an understanding of how to
manipulate materials properties and functionality through the control of the material’s
structure and processing techniques.
The most important aspect of materials is that they are enabling; materials
make things happen. For example, in the history of civilization, materials such as
stone, iron, and bronze played a key role in mankind’s development. In today’s fast-
paced world, the discovery of silicon
single crystals and an understanding of their
properties have enabled the information age.
In this book, we provide compelling examples of real-world applications of
engineered materials. The diversity of applications and the unique uses of materials
illustrate why a good engineer needs to understand and know how to apply the
principles of materials science and engineering.
1-1 What is Materials Science and Engineering?
Materials science and engineering (MSE) is an interdisciplinary field that studies and
manipulates the composition and structure of materials across length scales to control
materials properties through synthesis and processing. The term composition means the
chemical make-up of a material. The term structure means the arrangement of atoms,
as seen at different levels of detail. Materials scientists and engineers not only deal with
the development of materials, but also with the synthesis and processing of materials and
manufacturing processes related to the production of components. The term “synthesis”
refers to how materials are made from naturally occurring or man-made chemicals. The
term “processing” means how materials are shaped into useful components to cause
changes in the properties of different materials. One of the most important functions
of materials scientists and engineers is to establish the relationships between a material
or a device’s properties and performance and the microstructure of that material, its
composition, and the way the material or the device was synthesized and processed. In
materials science, the emphasis is on the underlying relationships between the synthesis
and processing, structure, and properties of materials. In materials engineering, the focus
is on how to translate or transform materials into useful devices or structures.
One of the most fascinating aspects of materials science involves the investigation
of a material’s structure. The structure of materials has a profound influence on many
properties of materials, even if the overall composition does not change! For example, if
you take a pure copper wire and bend it repeatedly, the wire not only becomes harder but
also becomes increasingly brittle! Eventually, the pure copper wire becomes so hard and
brittle that it will break! The electrical resistivity of the wire will also increase as we bend
it repeatedly. In this simple example, take note that we did not change the material’s com-
position (i.e., its chemical make-up). The changes in the material’s properties are due to a
change in its internal structure. If you look at the wire after bending, it will look the same
as before; however, its structure has been changed at the microscopic scale. The structure
at the microscopic scale is known as the microstructure. If we can understand what has
changed microscopically, we can begin to discover ways to control the material’s properties.
Let’s consider one example using the materials science and engineering tetrahedron
shown in Figure 1-1. (Another example is shown on the chapter opening page.) For most
of the history of commercial air travel, the fuselages of airplanes have been made using
aluminum alloys. The fuselage material must possess sufficiently high strength, but must
also be lightweight and formable into aerodynamic contours. Aluminum is one material that
meets these requirements. In 2011, passengers began traveling on Boeing’s 787 Dreamliner
aircraft. One of the primary innovations of the Boeing 787 is the extensive use of composites;
composite materials are formed by incorporating multiple components in a material in such
a way that the properties of the resultant material are unique and not otherwise attainable.
Composite materials comprise half of the Dreamliner’s total weight, and in fact, the fuselage
of the Boeing 787 is made from carbon fiber-reinforced plastic. Carbon fiber-reinforced
plastic is a composite of carbon fiber in a polymer epoxy resin matrix.
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Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.
1-1 What is Materials Science and Engineering? 5
●
How much can the weight of
the fuselage be reduced by using
Performance a composite?
Cost
●
What is the passenger capacity of
a composite fuselage airplane?
● What is the cost of fabrication? Is
the cost offset by fuel savings?
A: Composition
●
What material should be used
for the matrix?
●
What material should be used
as the reinforcing phase?
● What should the volume percentage
of the reinforcing phase be?
C: Synthesis and processing
● What process should be used to
fabricate the fuselage?
●
How can composite components be
joined?
●
Can the processing be implemented
with sufficient reliability?
B: Microstructure
● How should the reinforcing phase
be arranged in the matrix?
● What features of the structure
influence reliability?
●
What controls the strength?
Figure 1-1 Application of the materials science and engineering tetrahedron to carbon fiber-reinforced
plastic for the fabrication of aircraft fuselages. The composition, microstructure, and synthesis/
processing are all interconnected and affect the performance-to-cost ratio. Clockwise from upper
right: the Boeing 787; the interior of an empty Boeing 787 fuselage; a giant autoclave used to bake
carbon fiber-reinforced plastic sections; carbon fiber in an epoxy matrix. (Bloomberg via Getty Images /
Srinivasa, Vinod, Shivakumar, Vinay, Nayaka, Vinay, Jagadeeshaiaih, Sunil, Seethram, Murali, Shenoy,
Raghavendra, & Nafidi, Abdelhakim. (2010). Fracture morphology of carbon fiber reinforced plastic
composite laminates. Materials Research, 13(3), 417-424. Retrieved January 06, 2014, from http://www
.scielo.br/scielo.php?script=sci_arttext&pid=S1516-14392010000300022&lng=en&tlng=en. 10.1590/S1516
-14392010000300022./ AFP/Getty Images / Aviation Images)
After decades of success with their various models of aircraft, Boeing invested
billions of dollars to develop a commercial airplane based on a new class of materials.
Why would Boeing do this? The driving force behind the move to carbon fiber-reinforced
plastic was to reduce the weight of the fuselage, thereby increasing fuel efficiency. This
significantly increases the performance to cost ratio of the aircraft.
The switch to a composite material involved numerous technical challenges. What
would the composite material be? How would the composite fuselage be formed? Decades
of data are available for the growth of cracks in aluminum under the cyclic loading of
take-offs and landings. Would the composite fuselage be reliable? Would a carbon
fiber-reinforced plastic also have the corrosion-resistance that aluminum has or would
delamination between the fibers and plastic occur? Aluminum jets have structural panels
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Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.
6 Chapter 1 Introduction to Materials Science and Engineering
that are riveted together. How can various structural components made from composites
be joined? From this discussion, you can see that many issues need to be considered during
the design and materials selection for any product and that the ratio of performance to
cost, composition, microstructure, and synthesis and process are all critical factors.
Let’s look at one more example of the application of the materials science and
engineering tetrahedron by considering the use in microelectronic devices of a class of mate-
rials known as semiconducting polymers (Figure 1-2). Many types of displays such as those
found in alarm clocks and watches utilize light emitting diodes (LEDs) made from inorganic
compounds based on gallium arsenide (GaAs) and other materials; however, semiconduct-
ing polymers also have been used more recently. The advantages of using plastics for micro-
electronics include their flexibility and ease of processing. The questions materials scientists
and engineers must answer with applications of semiconducting polymers are
●● What are the relationships between the structure of polymers and their electrical
properties?
●● How can devices be made using these plastics?
●● Will these devices be compatible with existing silicon chip technology?
●● How robust are these devices?
●● How will the performance and cost of these devices compare with traditional
devices?
These are just a few of the factors that engineers and scientists must consider
during the development, design, and manufacturing of semiconducting polymer devices.
Figure 1-2 Application of the tetrahedron of materials science and engineering to
semiconducting polymers for microelectronics.
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Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.
