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```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.
AE Activity 2.1.1 Aerospace Materials Investigation – Page 1
Forces
Squeezing
Engineering term
(look above the
block)
Compression
Definition
Two examples of how this force
Compression is a force that
pushes a material closer together.
If the material squeezes to much the
length will be two short. It would also
make it denser.
Stretching
Tension
Tension pulls a material farther
apart.
If a material is stretched too thin it
has a greater possibility of breaking,
and the length would be too long.
Bending
Bending
Bending is where the top of the
material stretches apart, and the
bottom part compresses together,
resulting in a curve.
If a material bends to far it could
break.
Sliding
Shear
Where two sections of the material
slide past each other in opposite
directions.
If a material shears it will break.
Twisting
Torsion
Where the material twists.
The material could break if twisted to
far.
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
Tension
Compression
(Stretching) (Squeezing)
Aluminum
3
Steel
Cost
Weight
4
Applications
9
2
Light, doesn’t rust, strong in
compression and tension.
Expensive
Airplane wings, boats, cars.
7
9
Strong in compression and
tension.
Rusts, loses strength in extremely
high temperatures.
Cables, trusses, beams, and
columns.
2
3
Pros and Cons
Tension
9. Even though steel is an exceptionally strong metal, why wouldn’t it be a good choice for use inside jet engines?
It is very, very heavy.
AE Activity 2.1.1 Aerospace Materials Investigation – Page 3
Polymers
10. 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)
3
Cost
Weight
Pros and Cons
Applications
9
1.5
Flexible, light, long lasting, strong
in compression and tension.
Expensive
Umbrellas, inflatable roofs over
sports arenas.
3
11. 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?
It would not be very good, because its shape is easily changed.
Ceramics
12. 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
1
Strength in
Cost
Compression
(Squeezing)
3
2
Weight
Pros and Cons
Applications
4
Cheap, strong in compression.
Heavy, weak in tension.
Walls of early skyscrapers and
tunnels, domes.
do you think ceramics behave this way?
Compression. I think they behave this way because they are strong but brittle.
AE Activity 2.1.1 Aerospace Materials Investigation – Page 4
14. 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 are heavy and brittle.
15. Why wouldn’t brick be used to make the cables which hold up a suspension bridge? It isn’t flexible and would break easily.
Composites
16. 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
Reinforced
Concrete
Strength in Strength in
Cost Weight Pros and Cons
Tension
Compression
(Stretching) (Squeezing)
2
2
1
Cheap, light, moderately strong
3
in compression and tension.
Rots, swells and burns easily.
4
4
Applications
Bridges, houses, rollercoasters.
6
Low cost, fire and weather
Bridges, dams, domes, beams
proof, molds to any shape,
and columns.
2
strong in compression and
tension.
Can crack as it cools and
hardens.
17. 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?
Because they add strength to the material.
18. In your opinion, what would have happened if we would have pulled on the wood/reinforced concrete from the top and bottom
It would break easier because the steel rods and wood fibers wouldn’t add any strength in that direction.
AE Activity 2.1.1 Aerospace Materials Investigation – Page 5
19. 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.
It improves both tension and compression because they add to the concretes strength.
20. 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 are more prone to rot, and corrosion.
21. 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)
7.85 g/cc
747 MPa
19.2%
2.7 g/cc
>=276 MPa
8.0%
1.37 g/cc
36 MPa
282%
.36 g/cc
1.59 MPa
(AISI Type S14800
Stainless Steel condition
A)
Aluminum
(6061-T8)
Plastic
(PVC, Extruded)
Wood
(American Sitka Spruce)
22. 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.
Aluminum.
AE Activity 2.1.1 Aerospace Materials Investigation – Page 6
Conclusion
1. What role does material selection have in aerospace design?
It plays a big role because you need to choose a good material that is strong, light,
durable, and cheap.
2. Why would an aerospace designer specify an inferior material compared to other
materials if both materials meet the design specifications?
It may be cheaper.