Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Materials in Design > Composites > Flashcards

Composites Flashcards

1
Q

Definition of a Composite

A
  1. Combination of two materials in which one of the materials is called the reinforcing phase, which is embedded in the other material called the matrix phase.
  2. Materials made from two or more constituent materials with significantly different physical or chemical properties
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

General Advantages of Composites?

A
  1. Higher specific Strength
  2. Design Flexibility
  3. Corrosion Resistance
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What types of Reinforcing fibres are there?

A

Glass fibres, Carbon fibres, Boron fibres and Aramid(Kevlar) fibres.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Properties of Glass Fibres?

A
  1. Most common and least expensive

2. High Strength, low stiffness and high density

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Properties of Carbon Fibres?

A
  1. More expensive than glass fibres

2. Compared to glass fibres, lower in density, higher in stiffness and strength

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Properties of Boron Fibres?

A
  1. Consists of boron deposited on tungsten fibres
  2. High strength and stiffness in tension and compression
  3. Resistance to high temperature
  4. Heavy & expensive
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Properties of Aramid (Kevlar) fibres

A
  1. Highest specific strength
  2. Toughest fibre
  3. Undergoes plastic deformation before fracture
  4. Absorbs moisture and is expensive af
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Role of matrix?

A
  1. Binds fibres together
  2. Protects fibres
  3. Transfers loads to and from fibres
  4. Provides rigidity and shape to structure
  5. Isolate fibres to slow crack propagation
  6. Surface quality, corrosion and wear protection for fibres
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Demands on matrix?

A
  1. Interlaminar shear strength
  2. Toughness
  3. Moisture/Environmental resistance
  4. Processing Temperature
  5. Service Temperature
  6. Processing and cost
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Role of fibres?

A
  1. Carry the load
  2. Provide structural properties to composite, (strength and stiffness)
  3. Improve thermal stability
  4. Provide electrical conductivity or insulation
  5. Influences formability and machinability of composites
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Do long or short fibres provide higher effective stiffness & strengthening?

A

Long fibres

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Definition of rule of mixtures?

A

Predicts the density of a composite as well as other properties,

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Which loading (longitudinal/transverse) undergoes isostrain condition? With the other undergoing isostress condition

A

Longitudinal

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Is a composite weaker under longitudinal or transverse loading (with respect to fibre direction)?

A

Transverse

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

In what orientation is maximum strength of a long fibre obtained?

A

0 degrees, force parallel to fibre direction

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Advantages of carbon fibres?

A
  1. High Stiffness and strength
  2. Low density
  3. Intermediate cost
  4. Non-reactive
17
Q

Disadvantages of carbon fibres?

A

Low toughness, Brittle

18
Q

Which carbon fibre type is dominating the market?

A

Polyacrylonitrile (PAN)

19
Q

What is the process of processing carbon fibres?

A
  1. Precursor fibres stabilize at about 200-400C by an oxidation process
  2. Subject to high temperature treatment at around 1000C to remove hydrogen, oxygen, nitrogen and other carbon elements (This is called carbonization).
  3. Carbonized fibres can be further graphitized at even higher temperature (around 3000C) to achieve higher carbon content
20
Q

What are the three types of carbon fibre layer structures?

A
  1. Graphitic
  2. Turbostatic
  3. Hybrid Structure
21
Q

Which types of plastic can provide good wettability and why?

Why is it better than the other type?

A

Thermosetting polymer provides good wettability due to it’s low molecular weight of uncured resin.

This allows for high molecular mobility during processing.

Enables resin to quickly wet surface.

Thermoplastic has high molecular weight hence high viscosity at molten state, hence slower wetting.

22
Q

Which type of plastic has lower processing temperature?

A

Thermosets which can be cured from room temperature to 200C.

Thermoplastics typically has a range of 300-400.

23
Q

What are the difference in properties of a thermoplastic and a thermoset?

A

Thermoset - Hard, higher usage temperature

Thermoplastic - Soft, lower usage temperature

24
Q

What are the three most common thermosetting polymers?

A
  1. Phenolics
  2. Epoxies
  3. Polyester
25
Q

What is the fibre-matrix interface? Why is it important to have a strong interface?

A

Fibre-matrix interface determins the effective load transfer from the matrix to the fibre.

It affects crack propagation and load transfer. A strong interface means better load transfer.

Shear, transverse, flexural and impact tougness will be significantly influenced.

26
Q

What is essential to improve bonding between fibres and polymer in carbon fibre?

How is it done?

A

Surface treatment.

It involves oxidation treatment and the use of coupling agents, wetting agents, and/or sizing (coatings)

27
Q

Main drawbacks of using wet/hand layup process?

A

High viscosity leading to slow resin flow (leading to slow saturation). This is due to resin experiencing curing reactions while flowing in mould.

28
Q

Differences between layup and Resin Transfer Moulding?

A

Layup is open, whilst RTM is closed and vacuum assisted.

RTM is dry, whilst layup is wet.

Parts produced by RTM can have closer dimensional tolerances.

Layup is more versatile and

29
Q

What is a monocoque frame construction?

A

When the entire frame is laid up without individual tubes. The entire structure is moulded together.

30
Q

What is the influence of void in composites?

A

Void influences the initiation and propagation of cracks thus will effect failure of materials.

Increasing void content will decrease inter-laminar shear strength.

31
Q

Can we increase curing time of composite processing?

A

Extending cure time will not be harmful as the curing temperature is well below the thermal degradation temperature of the epoxy

32
Q

What is the affect of increasing curing temperature?

A

Higher temperatures produce a more complete reaction with a greater degree of cross-linking

33
Q

Does increasing the curing time at low temperatures yield similar results to curing at high temperatures?

A

Curing at lower temperature for a longer time does NOT always yield the same degree of cross-linking as high temperature curing.

Materials in Design (4 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions