Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

Engineering Materials > Composites > Flashcards

Composites Flashcards

1
Q

What are the two components of a composite?

A

Composites are made of two component, these are a fibre/filament reinforcement and a matrix.

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

What is the role of the matrix in the composite?

A

-Transfer load to the reinforcement
-Binds reinforcement together
-Protects the reinforcement

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

What is the definition of a composite?

A

Composites are heterogeneous material systems in which individual constituents retain their characteristics but are incorporated into a single structure to give a new material possessing superior properties to the constituent materials acting independently.

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

List the properties that can be improved by replacing monolithic materials with composites

A

Strength, stiffness, weight, fatigue life, corrosion resistance, wear resistance, temperature dependent behaviour and thermal insulation

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

What is the classification of composites by the type of matrix?

A

Polymer matrix composites (PMC) - Metal matrix composites (MMC) - Ceramic matrix composites (CMC)

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

What is the classification of composites by the type of reinforcement?

A

Particulate - Fibrous → Short fibres → Continuous fibres → Unidirectional- Woven/braided - Laminate

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Why do we use fibre reinforced composites (FRC’s)

A

Continuous fibres are inherently much stiffer and stronger than the same material in bulk form

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Why is fibre diameter important?

A

Smaller diameter fibres provide higher fibre surface areas, spreading the fibre/matrix interfacial loads but come at a greater price

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What are the ranges of FVF we expect in a composite?

A

Square packing: Vf=0.785
Hexagonal packing: Vf=0.907
In reality FVF is typically around 0.6 (lower due to manufacturing)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

In what directions are fibres designed to be loaded?

A

Fibres are designed to be loaded along their length, and not across their width

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Are FRC’s isotropic?

A

No, FRS’s are anisotropic materials. The properties of FRC’s are highly direction dependent on the direction within the material

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

How are carbon and graphite fibres produced?

A

They are produces by the controlled oxidation and carbonisation of carbon rich organic precursors (such as PAN polyacrylonitrile)

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

What are the important characteristics of carbon fibres?

A

-Bend easily and can be woven into fabric
-Have very low coefficients of thermal expansion
-Are anisotropic

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

What occurs during the graphitisation process of carbon fibre production?

A

The variation of the graphitisation process produces either high strength or high modulus fibres.

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

What are the groupings for carbon and graphite fibres?

A

-High strength (HS)
-intermediate modulus (IM)
-High modulus (HM)
-Ultra high modulus (UHM)

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

Are glass fibres isotropic?

A

Yes, glass fibres are isotropic

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What are the main characteristics for E-glass?

A

-Good strength, stiffness and electrical properties
-Resistant to water leaching

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What are the main characteristics for S-glass?

A

-It has higher strength, stiffness and temperature resistance

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Why are glass fibres treated with sizing?

A

Fibres are treated with a SIZE to minimise damage during manufacturing

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What is SIZE?

A

Size is a coating which both helps protect the glass filaments for processing as well as ensure proper bonging to the resin matrix.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What are aramid fibres?

A

Aramid is aromatic polyamide, this is most commonly known as kevlar.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

How are aramid fibres produced?

A

They are produced by spinning a solid fibre from a liquid blend

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What are the main characteristics for aramid fibres?

A

-Have high strength, low density, good resistance to impact

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

How are silicon carbide (SIC) fibres produced?

A

They are produced by the chemical vapour deposition of silicon and carbon core which turns them into titanium matrix composites (TMC’s)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
How are boron fibres produced?
Produced by the vapour deposition of boron on a tungsten wire and coating the boron with a thin layer of born carbide. They cannot be bent or woven into fabric.
26
What are the main properties of thermoplastic?
-They can be repeatedly softened by heating and hardened by cooling -Can be repaired and recycled
27
What are the main properties of thermosets?
-When heated, they form molecular networks -They degrade when heated but do not melt -Cannot be changed in form once they are set during curing -Cannot be reshaped by heating
28
What are the main properties of metal matrices (Al, Ti, Mg, Cu)?
-Usually ductile -Very reactive
29
What are the main properties of ceramic matrices?
-Offer much higher use temperature (2200C) -Very brittle, reinforcement is used to improve fracture toughness
30
What are the two types of ceramic matrices?
-Glass ceramics -Technical ceramics
31
What are the main properties of glass ceramics and how are they produced?
-Formed when glass is treated by heat and undergoes controlled crystallisation -It is a composite itself, made of glass and crystalline ceramics -Has superior mechanical properties to the parent glass and has easy fabrication
32
How are technical ceramics reinforced?
They are reinforced with whiskers and particles
33
What is prepreg?
Prepreg is a matrix preimpregnated unidirectional tape
34
What are the fabrication procedures for PMC's?
-Hand lay up -Vacuum bagging -Resin transfer moulding (RTM) -Filament winding -Pultrusion
35
Explain the hand lay up procedure
Fibres in the form of fabric are impregnated with resin by hang using brushes and rollers, the resultant composite is cured at atmospheric pressure
36
What materials can be used for hand lay up?
-Resins: any -Fibres: any, but heavy aramid fibres may be difficult to wet out
37
What are the main advantages of hand lay up?
-Wide choice of suppliers -Simple to teach -Low cost tooling -High FVF's
38
What are the main disadvantages of hand lay up?
-Skills dependent -High void content -Health and safety risk posed by resins
39
What are the typical applications of hand lay up?
-Wind turbine blades -Boats -Architectural mouldings
40
What is vacuum bagging?
This is an extension of the hand lay up method where pressure is applied to improve consolidation
41
What materials can be used for vacuum bagging?
-Resins: primarily epoxy -Fibres: A variety of heavy fabrics can be used
42
What are the main advantages of vacuum bagging?
-Higher FVFs (than with hand lay-up) -Lower void content -Better fibre wet-out (due to pressure) -Better health and safety (the vacuum bag reduces the amount of hazardous emissions)
43
What are the main disadvantages of vacuum bagging?
-Extra labour and material costs -Skills dependent control of mixing and resin content
44
What are the typical applications of vacuum bagging?
-Large cruising boats -Race car components
45
What is resin transfer moulding (RMT)?
Fabric is pre pressed to the mould shape and held together by a binder, after clamping resin is injected into the cavity.
46
What materials can be used for RMT?
-Resins: thermoset -Fibres: any
47
What are the main advantages of RMT?
-High FVF's -Good health and safety -Both sides have a moulded surface
48
What are the main disadvantages of RMT?
-Matched tooling is expensive and heavy in order to withstand pressure -Unimpregnated areas can occur -Generally limited to smaller components
49
What are typical applications of RMT?
Small but complex components
50
What is filament winding?
Fibre tows are passed through a resin bath before being wound onto a mandrel. Fibre orientation is controlled by the fibre feeding mechanism and rate of rotation of the mandrel
51
What are the winding patterns of filament winding?
-Helical -Circumferential -Polar
52
What materials can be used for filament winding?
-Resins: any -Fibres: any
53
What are the main advantages for filament winding?
-Very fast and economic -Good control of resin content -Fibre cost is minimised -Very good structural properties
54
What are the main disadvantages for filament winding?
-High mandrel costs for large components -Difficult to lay fibres along the length of a component -Convex shaped components only -Resins of low viscosity must be used
55
What are the typical applications for filament winding?
Primarily hollow, generally circular or oval sectioned components (tanks, pipes etc)
56
What is the pultrusion process?
Liquid resin mixture and reinforcing fibres are pulled through a heated forming die using a continuous pulling device. The hardening of the resin in initiated by the heat from the die.
57
What materials are suitable for pultrusion?
-Resins: generally epoxy, polyester, vinylester -Fibres: any
58
What are the main advantages for pultrusion?
-Very fast and economic -Very good control of resin -Fibre cost is minimised (taken from a creel) -Very good structural properties -Limited emissions due to enclosed resin impregnation area
59
What are the main disadvantages for pultrusion?
-High heated die costs -Constant cross section components only
60
What are the typical applications for pultrusion?
-Beams -Columns -Platforms -Decking -Girders

Engineering Materials (8 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions