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M6 > 6.3.1- Reinforcing Materials > Flashcards

6.3.1- Reinforcing Materials Flashcards

1
Q

Name the common reinforcing fibres in composite. (6 examples)

A 
Nomex
Fibreglass
Aramid
Kevlar
Carbon Fibre 
Graphite.
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2
Q

What material is a DuPont development, is an infusible, wholly aromatic polymer made only as a fibre?

A

Nomex.

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3
Q

What properties does Nomex have? (3 examples)

A

1) High thermal stability
2) Temp Resistant
3) Flame Resistant.

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4
Q

What type of clothing is Nomex used in?

A

Flame proof suits.

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5
Q

Nomex in contrast to its chemical isomer (twin) Kevlar has what property?

A

Radiation Resistance.

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6
Q

How is Nomex honeycomb made?

A

Nomex paper sheets and phenolic resin.

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7
Q

What is fibreglass made of?

A

Strands of molten silica gel then spun together and woven into cloth.

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8
Q

What makes fibreglass so popular? (2 examples)

A

1) Low cost

2) Wide range of applications.

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9
Q

What are two negative characteristics of fibreglass compared to other fibre materials?

A

1) weighs more

2) less strength.

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10
Q

Name the two types of fibreglass used in aircraft.

A

E-glass- electrically resistant

S-glass- High tensile strength.

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11
Q

What is the density of fibreglass?

A

2.1 g/cm³.

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12
Q

Does fibreglass have high fracture toughness?

A

Yes.

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13
Q

Does fibreglass have good ‘wet out’?

A

Yes.

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14
Q

What makes Aramid recognisable?

A

The fibres are bright yellow.

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15
Q

What company is Aramid the registered trade name to?

A

DuPont.

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16
Q

What is Aramid an ideal material for?

A

Parts subject to high stress and vibration e.g. rotor blades. Also used in bullet proof vests.

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17
Q

What is Aramid the shortened name form of?

A

Aromatic Polyamide.

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18
Q

What is damage to Aramid repaired with?

A

Fibreglass.

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19
Q

The word aromatic does not refer to the smell in fact it means…

A

a benzene compound.

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20
Q

What is the density of Aramid?

A

1.45 g/cm³.

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21
Q

To what temperature is Aramid heat resistant?

A

260°c.

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22
Q

Kevlar is another development from what company?

A

DuPont.

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23
Q

What is the description of Kevlar?

A

Man-made organic fibre with high tensile strength and flexibility.

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24
Q

What are some disadvantages of Kevlar? (3 examples)

A

1) fibres absorb moisture
2) ‘easily’ compressed
3) difficult to cut- special scissors and drill bits.

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25
Q

Kevlar is ultra-violet sensitive, what happens to the colour?

A

Goes from gold to brown.

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26
Q

What is the density of carbon fibre?

A

1.8 g/cm³.

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27
Q

What is the thermal extension in longitudinal direction of carbon fibre?

A

Nearly 0.

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28
Q

Name any of carbon fibres characteristics. (5 examples)

A

1) High Strength
2) High E-module
3) Low fracture resistance
4) High temp resistance
5) Electrically conductive

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29
Q

Black graphite/ carbon fibre is…

A

Strong and stiff and is used for its rigid properties.

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30
Q

What material is graphite stronger than in compressive stress.

A

Kevlar

However graphite is more brittle

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31
Q

What problem does graphite have when bonded with aluminium and what is the solution?

A

It is corrosive, so a layer of fibreglass must be used to isolate the two materials.

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32
Q

Give the definition of Warp.

A

Threads running the length of fabric.

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33
Q

Give the definition of Weft/fill.

A

Threads running the width.

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34
Q

Give the definition of Selvage Edge (Selvedge).

A

Tightly woven edge opposite to the warp that prevents unravelling of the weave.

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35
Q

Give the definition of Bias.

A

Diagonal threads at 45° to the warp. It allows the material to take contours. Material can be stretched along the bias but not any other direction.

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36
Q

Give the definition of Unidirectional Fibre.

A

The fibres that run in the direction of the warp. To hold them together there will occasionally be transverse threads.

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37
Q

Give the definition of Bi-directional fibre.

A

Fibres run in two or more directions. Normally warp threads outnumber weft threads.

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38
Q

Give the definition of Mats.

A

A mat of chopped fibres, it does not have the strength of uni or bi-directional.

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39
Q

What makes Fabric Weaves better than unidirectional.

A

They are more resistant to fibre breakout, there are different types of weaves.

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40
Q

Name the 4 different matrix (bonding) materials.

A

Thermoplastics
Thermosets
Epoxy Resins
Prepreg.

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41
Q

Give the definition of a matrix material.

A

A bonding material that surrounds the fibre to give strength and take shape.

42
Q

Newer matrix materials have what 4 characteristics?

A

1) Good stress distribution
2) Heat resistant
3) Chemical Resistant
4) Durable.

43
Q

What are most new matric materials?

A

Epoxy resins.

44
Q

Matrix’s are two part systems consisting of what?

A

Resin and a hardener (catalyst), which acts as a curing agent.

45
Q

Resins are a type of plastic and are in two categories, what are they?

A

Thermoplastics

Thermoset.

46
Q

Thermoplastics are heated to form a shape, is this shape permanent or not?

A

It is not permanent. So if you heat it again it’ll take a new shape.

47
Q

What max temperature can thermoplastics be used up too?

A

750°F.

48
Q

Give an example of a thermoplastic?

A

Acrylic.

49
Q

Thermosets use heat to form and the shape is set….

A

Permanently. An example of this is bakelite.

50
Q

What are epoxy resins used to bond?

A

Non-porous and dissimilar materials, like metal to composite.

51
Q

What are Prepregs?

A

Fabrics that already have resin in.

52
Q

How must prepreg be stored?

A

In a freezer to prevent the resin from curing.

53
Q

What is the central assembly of a composite called?

A

Core material.

54
Q

When the core is bonded between two thin-face sheets it provides what?

A

A rigid, lightweight component. It is known as sandwich construction.

55
Q

Why are there different types of foams for core materials?

A

Different applications.

56
Q

What is the biggest benefit to honeycomb?

A

Excellent strength to weight ratio.

57
Q

What materials can be used to make honeycomb?

A

Aluminium, Kevlar, carbon, fibreglass, Nomex or steel.

58
Q

What are the two methods of honeycomb fabrication?

A

Corrugation

Expansion.

59
Q

Give a simple description of the corrugation process for making honeycomb.

A

Materials are converted placing one layer at a time and then pulled to reveal the structure.

60
Q

Give a simple description of the expansion process for making honeycomb.

A

All bonds are made simultaneously rather than layer by layer.

61
Q

How many sides are in a honeycomb shape and why?

A

6 sides, providing a high strength to weight.

62
Q

In reference to honeycomb, what is the ribbon direction?

A

The direction in which it can be pulled apart.

63
Q

What happens if you pull a honeycomb perpendicular to its ribbon line?

A

It separates.

64
Q

What happens if you pull a honeycomb parallel to its ribbon line?

A

It doesn’t separate.

65
Q

Name some other core materials. (3 examples)

A

Styrofoam, urethane and wood.

66
Q

Name the 4 methods used to electrically bond composite components.

A

1) Flame spray
2) Bonding Jumpers
3) Aluminium wires woven into the top layer
4) Aluminium foil bonded to top layer.

67
Q

What is the purpose of paint? (Structurally not literally).

A

To seal a surface after manufacture or repair.

68
Q

Where would you find safety precautions for working with composites?

A

Material safety data sheet. (MSDS)

69
Q

What information will you find in the MSDS?

A

Health precautions
Flammability
Ventilation requirements
Information for doctors

70
Q

Explain a simple chain reaction process of making plastics.

A

Chains of monomers link to become a polymer. A catalyst is generally required.

71
Q

When was polymerisation first understood?

A

1930.

72
Q

During polymerisation one of the monomers double bonds are broken, what are these bonds called and what’s their purpose?

A

Valency bond, to form a link with the next monomer in the chain, thus making a polymer.

73
Q

Are there any by-products of polymerisation?

A

No.

74
Q

In polymerisation Ethylene becomes what?

A

Polyethylene. (PE)

75
Q

In polymerisation styrene becomes what?

A

Polystyrene. (PS)

76
Q

In polymerisation vinyl chloride becomes what?

A

Polyvinyl-chloride. (PVC)

77
Q

Different monomers can be polymerised together too, what is this called?

A

Copolymerisation.

78
Q

What are two examples of copolymerised products?

A

Styrene/ acrylonitrile (SAN)

Acrylonitrile/ butadiene/ styrene (ABS)

79
Q

Besides polymerisation, what are two other methods of making plastics?

A

Polycondensation

Polyaddition.

80
Q

Polycondensation does create by products, what are two examples of these?

A

Water

Hydrochloric acid.

81
Q

What commercial plastics are used made using polycondensation?

A

Bakelite resins (thermosets)
Nylon (Polyamides)
Polyester.

82
Q

How does polyaddition work (simple description only)?

A

There are no by products produced, but hydrogen gas atoms migrate making valence (spare) bonds.

83
Q

What two important plastics are made using polyaddition?

A

Polyurethanes

Epoxies.

84
Q

What are the benefits of adhesives? (4 examples)

A

1) Economical
2) Distribute stress
3) Eliminate fasteners
4) moisture and corrosion resistant.

85
Q

What 4 factors effect the adhesive bond?

A

Resistance to slip or shrink
Malleability
Cohesive Strength
Surface tension.

86
Q

What is the advantage of synthetic adhesives?

A

They can be used alone or to modify a natural adhesive, which gives them a wider range of applications.

87
Q

Where are thermosetting adhesives used?

A

Metallic bonding of aircraft parts as they are heat resistant.

88
Q

Where are thermoplastic resins used?

A

Bonding wood, glass, rubber, metal and paper.

89
Q

Aerosil is a white powder, what is it used as?

A

A thixotropic agent, combined with resin, lacquer and even toothpaste.

90
Q

Name 3 advantages of elastomeric adhesives.

A

1) Join dissimilar metals without galvanic corrosion
2) Provide same strength as welded joints
3) Provide noise reduction
There are a load more examples in the notes page 100.

91
Q

What do contact adhesives use to bond?

A

Atmospheric pressure.

92
Q

Solvent adhesives work by the solvent evaporating to cure, what is left behind to form the bond?

A

Plastics or resin.

93
Q

Dispersion adhesives contain resins dissolved in water solutions, what is an example of these.

A

Wood glue/paste.

94
Q

Film adhesives are similar to prepreg, what are they used to bond?

A

Metal to metal

Core to skin (composites)

95
Q

What does a supported film adhesive contain?

A

Woven nylon carrier.

96
Q

How must a film adhesive be stored?

A

Refrigerated at -18°c.

97
Q

What is the definition of micro balloons?

A

Hollow phenolic balls with a range of diameters of 10-300 microns. They are mixed into resins.

98
Q

How should resins be mixed?

A

In a wax free container adding accelerator to the resin base. It should take 3-5 minutes.

99
Q

What must you do if a resin base has been stored in a freezer?

A

It must be allowed to reach ambient temperature as its heavier when cold.

100
Q

What happens when you add a catalyst to resin?

A

It reduces the pot life.

M6 (14 decks)

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