L8 Polymers composites and ceramics

Question 1

Three main reasons to use plastics?

Answer 1

1. Good mechanical properties in relation to density
2. Easy to form
3. Cheap materials

Question 2

When polymer chains crossbond there are three different ways they can do this. What are they and what materials are bonds found in?

Answer 2

• Weak hydrogen bonds = Thermoplastics
• Some strong covalent bonds = Rubber
• Dens strong covalent bonds = Thermosetting

Question 3

Three types of polymeric materials?

Answer 3

1. Thermoplastics
2. Thermosettings
3. Rubber

Question 4

What happens when polymer is heated up

Answer 4

It has no distinct melting temperature and becomes gradually softer with higher temperature

Question 5

Four types of shaping thermoplastics?

Answer 5

Injection molding
Blow-forming
Vacuum forming
Extrusion

Question 6

How do you shape thermosettings?

Answer 6

Casting and hardening

Question 7

How do you shape rubber?

Answer 7

Forming and vulcanization (Vulcanization of a hardening form of rubber)

Question 8

Thermoplastics can be recycled (True/False)

Answer 8

True

Question 9

Thermosettings can be recycled (True/False)

Answer 9

False

Question 10

Rubber can be recycled (True/False)

Answer 10

False

Question 11

What are the properties of carbon fiber?

Answer 11

It is strong in the directions of the layers but weak between the layers.

Question 12

What are the properties of graphene? (3st)

Answer 12

• High conductivity
• Extremely good mechanical properties.
• High price and CO2 footprint

Question 13

What are the properties as glassfiber?

Answer 13

(Basically ordinary glass) (4st)
* Cheap and low CO2 footprint
* Isolator
* Brittle
* High compressive strength

Question 14

Mechanical properties and bindings of kevlar?

Answer 14

C-C bindings in the fiber direction
It is a strong material

Question 15

Properties and bindings of spectra/dynema?

Answer 15

C-C bindings in the fibre direction
It is a strong material

Question 16

What is the properties of a fiber? (2)

Answer 16

A fiber can have very good properties that are better than homgeneous materials.
It has a direction of its chemical bonds. (it is strong in that direction)

Question 17

What is requiered to use a fiber as an engineering material?

Answer 17

The fibre strings or planes must be held together, which will cause it to be a composite.

Question 18

What are the two main fibers used?

Answer 18

Ceramic and polymeric

Question 19

What is a laminate?

Answer 19

A composite built up from fiberplanes (lamellas) with different directions. This causes it to be strong in all directions.

Question 20

What is a matrix in a composite?

Answer 20

The material that binds
together, usually a plastic (even
metal or ceramic)

Question 21

What are reinforcements in a composite?

Answer 21

Strong material added to make the composite stronger

Question 22

What are distance materials?

Answer 22

It is a material added to increase bending stiffness such as polymer foam.

Question 23

Four upsides up composites?

Answer 23

• Can use fiber properties
• Often low density
• Can provide good crime toughness
• Can control properties

Question 24

Three downsides of composites?

Answer 24

Manufacturing becomes more difficult and expensive
More difficulty in predicting properties
Difficult to recycle

Question 25

What is a ceramic?

Answer 25

A compound of metal and non-metal with strong bonds between them (Covalent/ion bonds)

Question 26

Properties of ceramics? (4)

Answer 26

Thermal and electrical isolator
Brittle
High melting temperature
Much better strength in tension than compression

Question 27

Properties of clay?

Answer 27

Strong bindings in the layers, weak inbetween.
Formable when wet

Question 28

What is a techninc cheramic?

Answer 28

Pure cheramics with solved additives?