Activity 2.1.1 Aerospace Materials
Investigation
Introduction
Within aerospace design, material selection has a large impact on overall design
performance as well as production and maintenance costs. Aerospace designers
and developers must always be aware of the impact that material selection has on
design specifications ranging from propulsion requirements to environmental factors.
In this activity you will investigate properties of materials in several categories.
Within each category you will consider the suitability of the materials in aerospace
applications.
Equipment



Computer with Internet access
Engineering notebook
Pencil
Procedure
1. Open the PBS Forces Lab at the following link :
http://www.pbs.org/wgbh/buildingbig/lab/forces.html
2. Click the Forces tab along the top.
3. Click Squeezing option. Click and drag the slider and observe the effect on the
material.
4. Observe images by clicking See It In Real Life.
5. Repeat this exploration for each force and use what you learned to complete the
following table.
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AE Activity 2.1.1 Aerospace Materials Investigation – Page 1
Forces
Engineering term
(look above the
block)
Definition
(in your own words)
Two examples of how this force
can affect airplanes (your ideas)
Squeezing
Compression
It is pressing inward on the 2
sides of the material
The wind against the steel and the
wings when air goes faster below it
Stretching
Tension
Pulling outward on the 2 opposite
sides
When the propeller pulls the airplane
forward and the wings pulls back.
Bending
deflection
It is when one side squeezes
together and the other apart
The g loading airplane structure
experiences when maneuvering,
when pulling up.
Sliding
Shear
Making 2 parts of the material slide The bolts that hold the aluminum skin
past each other
or the wings
Twisting
Torsion
It is to move 2 sides of a material
moving in opposite ways
During maneuvers
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AE Activity 2.1.1 Aerospace Materials Investigation – Page 2
6. Now that you understand forces, let’s observe various materials used in aerospace applications. Click on the tab labeled
Materials.
Metals
7. Click on each material shown below and move the slider until the material cracks. Use the tick marks on the scale to assign a
number to the force, cost and weight. Record this number on the following table. Move the slides completely to the maximum to
see a message about the material. Complete the table below using what you learn.
Type of
Material
Strength in
Strength in
Cost
Tension
Compression
(Stretching) (Squeezing)
Aluminum
-4
9
Weight
Pros and Cons
Applications
2
Pros;Lightweight, doesn't rust, strong in
compression and tension
Cons:
Airplane wings, boats, cars, skyscraper
"skin"
Cons; Expensive
9
Pros: One of strongest materials used in
construction, strong in compression and
tension,
Cons: Rusts, loses strength in extremely
high temperatures
Cables in suspension bridges, trusses, beams
and columns in skyscrapers, roller coasters
4
Steel
-3.5
4
6.8
8. Based on your results, in which loading condition (tension or compression) are metals strongest?
In compression aluminum is stronger but in tension steel is stronger
9. Even though steel is an exceptionally strong metal, why wouldn’t it be a good choice for use inside jet engines?
It is extremely heavy
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AE Activity 2.1.1 Aerospace Materials Investigation – Page 3
Polymers
11. Click on the material shown below and move the slider until the material cracks. Use the tick marks on the scale to assign a
number to the force, cost and weight. Record this number on the following table. Move the slides completely to the maximum to
see a message about the material. Complete the table below using what you learn.
Type of
Material
Strength in
Tension
(Stretching)
Plastic
Strength in
Compressio
n
(Squeezing)
-4
Cost
Weight
Pros and Cons
Applications
9
1.4
Strengths: Flexible, lightweight, longlasting, strong in compression and tension
Weaknesses: Expensive
Umbrellas, inflatable roofs over sports
arenas
3.5
12. As noted in the investigation, plastics are strong and very light, both of which are desirable characteristics to engineers.
However, watch carefully as you apply tension and compression to the plastic. Note how it behaves. Based on your
observations, would plastic be a suitable alternative to aluminum for airplanes, or steel for buildings? Why or why not?
Ceramics
13. Click on the material shown below and move the slider until the material cracks. Use the tick marks on the scale to assign a
number to the force, cost and weight. Record this number on the following table. Move the slides completely to the maximum to
see a message about the material. Complete the table below using what you learn.
Type of
Material
Strength in
Tension
(Stretching)
Brick
Strength in
Cost
Compression
(Squeezing)
-4
2.1
Weight
Pros and Cons
Applications
3.9
Strengths: Cheap, strong in compression
Weaknesses: Heavy, weak in tension
Walls of early skyscrapers and tunnels,
domes
1.5
14. Based on your observations, in which method of loading (tension or compression) are ceramics strongest? In your opinion, why
do you think ceramics behave this way? Ceramics behave best in compression. They spread force equally
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AE Activity 2.1.1 Aerospace Materials Investigation – Page 4
15. Since ceramics can be so strong (and relatively inexpensive), why aren’t they used to make aircraft or other transportation
machines? Why do we only seem them used in buildings or structures?
Because they can’t handle the elements as well as metals
16. Why wouldn’t brick be used to make the cables which hold up a suspension bridge?
Because steel is a better choice compared to it
Composites
17. Click on each material shown below and move the slider until the material cracks. Use the tick marks on the scale to assign a
number to the force, cost and weight. Record this number on the following table. Move the slides completely to the maximum to
see a message about the material. Complete the table below using what you learn.
Type of
Material
Wood
Strength in Strength in
Cost Weight Pros and Cons
Tension
Compression
(Stretching) (Squeezing)
Strengths: Cheap, lightweight, moderately
-3
2.1
1
strong in compression and tension
Weaknesses: Rots, swells and burns easily
3
Reinforced
Concrete
4
-4
4.5
5.9
Strengths: Low cost, fireproof and
weatherproof, molds to any shape, strong in
compression and tension
Weaknesses: Can crack as it cools and
harden
Applications
Bridges, houses, two- to three-story
buildings, roller coasters
Example: Son of Beast -- Cincinnati, Ohio
Bridges, dams, domes, beams and columns in
skyscrapers
Example: Hoover Dam - Nevada/Arizona
border
18. Note the arrangement of the steel rods in the reinforced concrete and the fibers of the wood. Why were these materials strongest
pulled along the rods and fibers?
The steel rods inside help spread the force
19. In your opinion, what would have happened if we would have pulled on the wood/reinforced concrete from the top and bottom
instead of the sides? Why?
It would be harder to pull apart. Because the forces would be spread out even easier, and there’s less space for cracks
© 2011 Project Lead The Way, Inc.
AE Activity 2.1.1 Aerospace Materials Investigation – Page 5
20. Click on the unreinforced concrete and perform a tension/compression test. How does adding the steel rods improve the strength
of the concrete (and in which mode, tension or compression)? Explain.
The steel rods handle a lot of the tension and spread it well across the concrete
21. As noted in the investigation, wood and reinforced concrete are relatively strong and inexpensive. Why don’t we use these
particular composite materials to construct aircraft or other transportation vehicles?
They cant handle the elements and aren’t strong enough,
22. The PBS Forces Lab is a resource designed to show qualitative comparisons between broad material categories. Engineers
need accurate material properties to design safe and predictable products. These material properties were measured using
stringent testing standards. These properties are published in sources for reference such as MatWeb http://www.matweb.com.
Use this site or a similar site to find properties of the materials shown below.
Material
Steel
Density or Specific Gravity
Tensile Strength
Elongation at Break
(Yield)
(if available)
7.70 g/cc
450 MPa
20 %
2.70 g/cc
>= 276 MPa
8.0 %
8.96 MPa
475 %
(AISI Type S14800
Stainless Steel condition
A)
Aluminum
(6061-T8)
Plastic
1.15 g/cc
(PVC, Extruded)
Wood
0.310 - 0.360 g/cc
1.59 MPa
(American Sitka Spruce)
23. Based on the information from the table rank the material for selection for an aircraft material choice for best strength to weight
ratio. Use density as a substitute for weight. Show calculations.
wood .310/1.56= 0.1987179487179487, plastic 1.15/8.96= 0.1283482142857143, steel7.7/450=
0.0171111111111111,Aluminum 2.70/276= 0.0097826086956522,
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AE Activity 2.1.1 Aerospace Materials Investigation – Page 6
© 2011 Project Lead The Way, Inc.
AE Activity 2.1.1 Aerospace Materials Investigation – Page 7
Conclusion
1. What role does material selection have in aerospace design?
It can lead to the most efficient design
2. Why would an aerospace designer specify an inferior material compared to other
materials if both materials meet the design specifications?
If it costs less then its more suitable.
© 2011 Project Lead The Way, Inc.
AE Activity 2.1.1 Aerospace Materials Investigation – Page 8
© 2011 Project Lead The Way, Inc.
AE Activity 2.1.1 Aerospace Materials Investigation – Page 9