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Part 66 Module 6 > Module 6.3.1 Composites > Flashcards

Module 6.3.1 Composites Flashcards

1
Q

What is the definition of a composite material?

A

Two or more materials that when combined create a much stronger material that each one by themselves.

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2
Q

What are the two components of a composite?

A
  • The matrix, hardener
  • The fabric/reinforcing material
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3
Q

What type of structure are modern composites used on in aircraft?

A

Primary structures.

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4
Q

List 3 advantages of composites.

A
  • High strength to weight ratio
  • Stress transferred through the fibres
  • Longer service life than metal
  • High corrosion resistance
  • 4x strength of steel
  • 6x strength of aluminium
  • Greater design flexibility
  • No joints or fasteners needed
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5
Q

List 3 disadvantages of composite materials.

A
  • Difficult to inspect
  • lack of long term data
  • High production and repair costs
  • Processing equipment is expensive
  • Lack of repair knowledge
  • Materials used are often hazardous
  • Lack of standard methods
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6
Q

Name all 5 reinforcing fibres used for composite materials.

A
  • Carbon fibre
  • Kevlar/aramid
  • Fibreglass
  • Ceramic
  • Boron
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7
Q

What colour is aramid?

A

Yellow/gold

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8
Q

What colour does aramid go when exposed to UV rays?

A

Brown

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9
Q

How can aramid be protected from lightning strikes?

A

A conductive weave in the fibres.

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10
Q

List 3 advantages of aramid.

A
  • Low density
  • Very flexible
  • High tensile strength
  • Heat resistant up to 260C
  • Not flammable or fusible
  • Good chemical and abrasion resistance
  • High toughness
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11
Q

What type of strength is weak aramid?

A

Compressive

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12
Q

List the disadvantages of aramid.

A
  • Poor compressive properties
  • Difficult to reshape
  • Wears out cutters
  • UV susceptible
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13
Q

What is the carbon fibre also referred to as?

A

Black graphite

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14
Q

List 3 advantages of carbon fibre.

A
  • Low density
  • High strength
  • Low fracture resistance
  • close to zero thermal extension
  • High temp resistance
  • Good electrical conductor
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15
Q

List the disadvantages of carbon fibre.

A
  • Wears out cutters
  • Brittle
  • Corrosive with aluminium
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16
Q

Why is boron not commonly used on aircraft?

A
  • Very expensive
  • Hazardous
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17
Q

Why would boron be used on aircraft? (4)

A
  • High tensile strength
  • High stiffness
  • Very hard wearing
  • Excellent compressive strength
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18
Q

What applications are ceramics used in?

A

High temperature

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19
Q

Where would ceramics be found on an aircraft?

A

Firewalls

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20
Q

What temperature do ceramics maintain their strength too?

A

1200C

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21
Q

What are the 4 keys terms in fabric orientation?

A
  • Warp
  • Weft
  • Bias
  • Selvedge edge
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22
Q

What orientation does the warp run in?

A

‘Wrap’ length ways as the material is unrolled.

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23
Q

At what angles do the warp, weft and bias run?

A

0, 90, 45 respectively.

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24
Q

What is the purpose of the selvedge edge?

A

Tightly woven edge running parallel to the warp. Stops fibres from unravelling.

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25
Q

Is the selvedge edge used in the final hardened product?

A

The selvedge edge gets cut off.

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26
Q

Why is a quasi-isotropic lay up is used?

A

To distribute forces evenly through many different angles.

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27
Q

What weave has the lowest crimp?

A

Satin weave

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28
Q

What weave has the highest crimp?

A

Plain weave

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29
Q

How are mats produced?

A

Chopped fibres pressed together. A light adhesive may be used. Not as strong as uni or bi-directional fibres.

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30
Q

What are the two general plastic categories?

A
  • Thermosetting
  • Thermoplastic
31
Q

Can thermoplastics be reheated and remoulded?

A

Yes they can.

32
Q

Can thermosets be reshaped?

A

No they can’t.

33
Q

What are Pre-pregs?

A

Pre-pregs come from the manufacturer and already have the correct amount of resin mixed.

34
Q

What precautions must be taken when using pre-pregs?

A

Must be stored in a freezer to prevent curing. Must be warmed to room temperature before use. The out-of-freezer time must be recorded.

35
Q

Why is pre-preg expensive?

A

Manufacturers only sell it in large quantities.

36
Q

What are the two types of reinforced composites?

A

Laminated and sandwich

37
Q

What is a laminated composite?

A

Multiple layers of reinforcing material bonded together and embedded in a resin matrix. Multiple layers are used to get desired thickness. Often at angles to each other. Can be made up of two or more different composite fibres.

38
Q

What is a sandwich composite?

A

A core bonded between to fibreglass sheets.

39
Q

Is the sandwich composite stronger than the laminated composite?

A

Yes it is. 10x stronger for only 6x the weight.

40
Q

What are the two most common types of core material in sandwich composites?

A

Honeycomb and foam.

41
Q

Why mustn’t plastic pipes be marked with heated dyes?

A

Pipes are already thin. By applying heated dyes you run the risk of melting the outer wall.

42
Q

Can one part sealants be used straight from the manufacturer?

A

Yes they can.

43
Q

How are thermosetting plastics marked?

A

They are marked using vitro-etching, white paint or ink.

44
Q

How should transparent plastics be marked?

A

Marking should be avoided. If there is a metal outer housing then it should be marked there. If not then a stencil and light sand-blasting should be used.

45
Q

How can thermoplastics be marked?

A

Heated dyes

46
Q

How do you make two part sealants ready for use?

A

Mix the base and accelerator in equal quantities.

47
Q

Where must film adhesives be stored?

A

In a freezer.

48
Q

Why must film adhesives be stored in the freezer?

A

As they will cure if left at room temperature.

49
Q

What is disbonding?

A

Separation of two elements. Can lead to delamination.

50
Q

What is delamination?

A

Forms on the boundary layer between different layers and causes layer separation.

51
Q

What are the 7 types of NDT?

A
  • Visual inspection
  • Audible testing
  • Ultrasonic inspection
  • Radiography
  • Thermographs
  • Dye penetrants
  • RF detector
52
Q

What problems can occur with tap testing?

A

Not even pressure of taps, so areas may sound different.

53
Q

In tap testing, what must the tester know about the area?

A
  • What it should sound like.
  • Position of structural supports.
54
Q

What are the 4 types of ultrasonic inspections?

A
  • Through transmission
  • Pulse-echo
  • Ultrasonic bond tester
  • Phased array
55
Q

In radiography, what area of the material appears white?

A

High density areas.

56
Q

How is a thermograph test conducted?

A

By passing heat from, to or through the tea object and measuring/mapping the differences in conductance.

57
Q

How is a dye penetrant test conducted?

A

Apply the dye all over the area. Then wipe off and spray with a dry talcum powder. This draws out the dye and reveals where the micro cracks are.

58
Q

Can dye penetrant tests be used on composites?

A

No they can’t, unless stated by the AMM.

59
Q

How does an RF test work?

A

Measures Rf power loss caused by the presence of water.

60
Q

Damage can be classified into 3 categories what are they?

A
  • Negligible
  • Repairable
  • Non-repairable
61
Q

Where can water ingress be a problem?

A

Inside the honeycomb cores

62
Q

How can a surface be tested to see if it has been sufficiently cleaned?

A

Water-break test

63
Q

Where can the procedure for a structural repair be found?

A

In the Structural Repair Manual SRM

64
Q

Do fastened repairs restore the same structural strength?

A

No they don’t. It also worsens streamlining.

65
Q

What fasteners are used in a fastened repair?

A

Blind fasteners

66
Q

What overlap should be given in a fastened repair?

A

1 inch

67
Q

In a potted repair what should the overlap be?

A

1 inch

68
Q

In a potted repair what should the undercut be?

A

1/8 inch

69
Q

Where should resin injection repairs be used?

A

In areas of minor delamination

70
Q

When doing laminate repairs what should the step cut overlap be?

A

1/2 inch

71
Q

When doing laminate repairs what should the top layer overlap be?

A

1 inch

72
Q

What is crazing?

A

When plastic is under load small surface fissures can occur.

73
Q

How do you restore surface finish on plastics after scratches?

A

Polishing, buffing.

74
Q

How can further propagation of cracks be halted?

A

Stop drilling

Part 66 Module 6 (4 decks)

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