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M6 Resit > 6.3 Composite Materials✅(8) > Flashcards

6.3 Composite Materials✅(8) Flashcards

1
Q

What is meant by ‘composite’

A
  • Describe 2 or more materials that are combined to form a stronger structure
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2
Q

The simplest composite is composed of two elements which are

A
  • Matrix (adhesives or resins)
  • A reinforcing material (fabric)
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3
Q

What are the most commonly used reinforcing fibres in the aviation industry?

A
  • Fibreglass
  • Aramid
  • Black graphite/carbon fibre
  • Boron
  • Ceramic
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4
Q

Fibreglass is now the most widely used composite material (T or F)

A

T

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5
Q

What are the advantages of fibreglass

A
  • generally less expensive than other composites
  • does not conduct electricity
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6
Q

2 common types of fibreglass?

A
  • E glass
  • S glass
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7
Q

What are the 2 types of Aramid (Kevlar)?

A

Kevlar 49 and Kevlar 29

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8
Q

How are Boron fibres made?

A
  • applying small amount of vapourised boron onto the tungsten or carbon wire (core)
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9
Q

What are the disadvantages of boron fibres?

A
  • very expensive
  • hazardous for maintenance personnel
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10
Q

Is boron fibres mostly used for commercial aviation or military?

A
  • military
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11
Q

Where are ceramic fibres used?

A
  • Where a high temperature application is needed
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11
Q

What are aircraft firewalls sometimes manufactured from

A

-Ceramic fibre composites

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12
Q

explain warp (relating to fabric orientation)?

A
  • threads run along the length of the fabric
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13
Q

Usually the fabric is stronger in the warp direction or weft direction?

A
  • Warp
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14
Q

explain weft/fill?

A
  • weft fibres run perpendicular to the warp fibres
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15
Q

explain selvedge edge?

A
  • tightly woven edge that runs parallel to the warp threads
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16
Q

What is the function of the selvedge edge?

A
  • prevents edges from unravelling
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17
Q

What is bias?

A
  • fibre orientation that runs at a 45* angle to warp threads
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18
Q

what is unidirectional materials?

A
  • major fibres run in warp direction
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19
Q

what is Bidirectional fibre?

A
  • fibres run in 2 or more different directions
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20
Q

Chopped fibres that are compressed together are often called?

A

‘mats’

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21
Q

What are the most common weaves

A
  • Plain weave
  • Twill weave
  • Satin weave
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22
Q

What are thermoplastics

A
  • Use heat to form the part into the desired shape.
  • Shape is not permanent (reversible)
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23
Q

Are epoxy resins classed as thermosetting plastic resins (T or F)?

A

T

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24
Q

What is pre-impregnated fabrics known as ?

A

Pre-pregs

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25
Q

What is pre-impregnated fabric?

A
  • fabric that have the correct amount of resin already saturated on fabric
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26
Q

Pre-impregnated materials are made to eliminate what?

A
  • any error during the mixing and application process
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27
Q

What would happen to resin systems in pre-preg materials if not kept in cold storage?

A

It will start to cure

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28
Q

What are laminated composites?

A
  • consists of 2 or more layers of reinforcing material bonded together
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29
Q

What are sandwich composites?

A
  • core bonded between 2 thin fibreglass sheets
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30
Q

Typical applications of sandwich composites?

A
  • flying control surfaces
  • wing to body fairings
  • helicopter rotor blades
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31
Q

Sandwich composite is at least 10x stronger than laminate, and the weight is only increased by 6x (T or F)

A

T

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32
Q

What are the 2 most common types of core materials used in sandwich construction?

A
  • honeycomb
  • foam
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33
Q

What are core materials

A
  • central members of an assembly
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34
Q

honeycomb refers to how a material is constructed to combine high stiffness with low weight (T or F)?

A

T

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35
Q

Honeycomb cores have an excellent strength to weight ratio (T or F)?

A

T

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36
Q

What are thermosetting plastics?

A
  • When heated and cooled, it fully cures (cannot be reshaped)
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37
Q

What is the newest type of transparent plastics?

A
  • stretched acrylic
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38
Q

Monolithic plastic sheets are made

A
  • in single solid uniform sheets
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39
Q

Laminated plastic sheets are made

A
  • from transparent plastic face sheets bonded by inner layer of clear resin material
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40
Q

What is a one part sealant ?

A
  • prepared by manufacturer
  • ready for application
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41
Q

What is a two part sealat?

A
  • Require separate packaging to prevent curing prior to applications
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42
Q

What is a specialised form of adhesive known as

A

‘film adhesive’

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43
Q

What happens if you store the film adhesive in a freezer?

A
  • Curing process slows down (increases shelf life)
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44
Q

What materials are prone to erosion

A

Composite materials

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45
Q

How are composite materials protected from ultraviolet (UV) light?

A

-special UV primers and paints

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46
Q

What is the primary inspection for all in service inspections of composites

A

visual inspection

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47
Q

What is audible testing (coin/automated tapping)?

A
  • tapping defective area and listening for any change of sound
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48
Q

In what circumstance is the audible testing not reliable?

A
  • structure with more than 4 piles
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49
Q

What is ultrasonic inspection?

A

-sound wave energy with a frequency above the audible range

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50
Q

what is the best method to detect internal delamination

A

ultrasonic inspection

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51
Q

What is radiography inspection

A
  • often referred to as X-ray
  • allows a view into the interior of the part/component
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52
Q

What is a thermograph inspection

A
  • heat sensing devices used to measure temperature variations
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53
Q

What is dye penetrants used to detect?

A
  • cracks and other defects in metallic surfaces
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54
Q

Should dye penetrants be used on composite structures?

A
  • No, it should not be used unless manufacturer stated
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55
Q

What is a moisture detector?

A
  • detects water in sandwich honeycomb structures
56
Q

How does the moisture detector work?

A
  • meter measures the RF power loss caused by the presence of water
57
Q

What is a cosmetic defect

A
  • defect on outer skin (does not involve damage to structure)
58
Q

What are the 3 classifications of damage

A
  • Negligible
  • Repairable
  • Non- repairable
59
Q

What is impact damage

A
  • when a foreign object strikes the part
60
Q

What is delamination?

A

separation of fabric layers of material in a laminate

61
Q

What does it mean by ‘disbonds’?

A
  • separation of the composite materials from another material to which it has been bonded
62
Q

The separation between the skin and core of composite sandwich structure is referred as?

A

core disbond

63
Q

What are the 5 basic types of composite repairs

A
  • Pre-cured patches
  • Potted
  • Resin injection
  • Laminate repair (one surface)
  • Laminate repair (through part)
64
Q

A temporary repair can be performed to cover holes or deep scratches by using what?

A

pre-cured patch installed with blind fasteners/adhesive

65
Q

Potted repairs are restricted to what structures and how much damage tolerance?

A
  • honeycomb core sandwich structures
  • damage up to 2.5cm (1in) in diameter
66
Q

How can minor delamination be repaired?

A

-Resin injection (potting compound)

67
Q

Honeycomb sandwich structures are prone to what damage

A
  • Impact damage
  • Puncture damage
68
Q

What are the 2 more common honeycomb sandwich structure repair?

A
  • puncture repair
  • honeycomb core repairs
69
Q

What are the 2 commonly used solvents in composite repair?

A
  • Methyl-Ethyl-Ketone (MEK)
  • Acetone
70
Q

Methyl-Ethyl-Ketone (MEK) is commonly used for cleaning dust and grease from composite components (T or F)?

A

T

71
Q

Acetone is used for general equipment and tool equipment (T or F)?

A

T

72
Q

What are the 4 major types of plastic failure?

A
  • Environmental failure
  • Thermal failure
  • Chemical failure
  • Mechanical failure
73
Q

What is crazing?

A
  • when subjected to load, plastic materials develop small surface fissures
74
Q

How is crazing caused

A

improper installation, machining, or cold forming

75
Q

What is buffing?

A
  • remove fine, hairline scratches
  • final polishing process
76
Q

When sanding, water/detergent must be used as a lubricant to prevent the paper from becoming clogged (T or F)?

A

T

77
Q

How can cracks be limited?

A

stop drilling

78
Q

An adaption of the truss-type wing is the ‘box spar’ (T or F)

A

T

79
Q

What loads does a box spar accept

A

-torsional and bending loads

79
Q

What is the most common wood used for aircraft structure

A

Sitka spruce

80
Q

To meet the Sitka spruce grade specifications, the wood must be kiln-dried(T or F)

A

T

81
Q

What is the maximum slope of grain that is acceptable when carrying out a wood assessment

A
  • 25mm-380mm (1inch-15inches)
82
Q

Aviation wood is usually quarter-sawn to reduce the amount of shrinkage over the lifetime of the component (T or F)?

A

T

82
Q

Most wood damage is caused by what conditions?

A
  • moisture
  • temperature
  • sunlight
83
Q

How can wood be protected from the attack of decay fungi, harmful insects, or marine borers?

A

by applying chemical preservatives

84
Q

How much strength does wood approximately lose at temperatures of 50*c

A

25%

85
Q

End grain portions of wooden members are much more absorbent than side grain (T or F)

A

T

86
Q

Excessive moisture at bolt holes promotes what

A

corrosion of the bolts

87
Q

How can sealing of wood surfaces in bolt holes be accomplished

A
  • varnish or other acceptable sealer
88
Q

What is a knot

A

identifies a point where a branch grew from the trunk of the tree

89
Q

Which knots are not acceptable for aircraft construction or repair

A

spike knots

90
Q

What are pitch pockets

A
  • small openings (weaken the wood)
91
Q

When are pitch pockets acceptable

A

centre portion of beam

92
Q

Can wood that has been compressed, be used in aircraft construction or repair?

A

No

93
Q

What does it mean by ‘compression failure’

A
  • tree falls and lands across a log or uneven ground
94
Q

How is decay caused

A

fungi that grows on damp wood

95
Q

Can stains or decay be used in aircraft construction or repair

A

No

96
Q

What is dry rot?

A

-brown rot decay caused by fungi

97
Q

How do you prevent dry rot

A
  • ensure kiln-dried wood with a moisture content of 20% or less is used
  • good surface finish (varnish, paint)
98
Q

What is Casein glue

A
  • powdered glue made from milk
    -deteriorates over the years it is exposed to moisture and temperature
99
Q

Casein glue is considered low grade and has become obsolete for all aircraft repairs (T or F)

A

T

100
Q

What is plastic glue also known as

A

urea-formaldehyde adhesive

101
Q

Plastic resin glue has been considered obsolete for all aircraft repairs (T or F)?

A

T

102
Q

Does plastic glue deteriorate when exposed to moisture and warm humid environments?

A

yes

103
Q

What is a Resorcinol glue

A
  • 2 part synthetic resin glue which consists of a resin and a hardener
104
Q

Which glue is the most water resistant

A

Resorcinol glue

105
Q

Which glue is most commonly used on repairs of aircraft wooden structures

A

Resorcinol glue

106
Q

What is epoxy resin

A
  • 2 part synthetic glue (consists of a resin and a hardener)
107
Q

Wood pieces that are joined, must be kept at a constant temperature for a minimum of how many hours

A

24 hours ( so moisture content can equalise)

108
Q

When testing a joint sample, the fractured glue must show at least 75% of wood fibres, evenly distributed over the fractured glue surfaces (T or F)

A

T

109
Q

What are the inspection methods for wooden structures

A
  • Non destructive
  • Destructive
110
Q

what must always be the first reference for any repair scheme?

A
  • AMM
111
Q

What is the simplest method to repair a small hole in plywood

A

a fabric patch

112
Q

What did nitrate dope help with

A

-tighten and stiffen the fabric

113
Q

What was the drawback of nitrate dope

A

extremely flammable

114
Q

To address the flammability issues, what dope was used

A

butyrate dope

115
Q

Why did they add aluminium solids to butyrate coatings?

A
  • as it reflected the suns rays, preventing UV damage
116
Q

All materials used for fabric covering, have to be stored at temperatures above what

A

20c (68F)

117
Q

What are the 2 types of fabric testers

A
  • Maule punch tester
  • Seyboth punch tester
118
Q

Seyboth and Maule fabric strength testers are designed for cotton and linen covered aircraft (T or F)

A

T

119
Q

How should fabric cracks be corrected?

A
  • sealed
  • replace
120
Q

What is the most common honeycomb construction in the aviation industry

A

Aramid paper

121
Q

Does a composite repair restore the full strength characteristics of the original structure

A

No

122
Q

What are resin injection or potted repairs used to repair

A

Small holes

123
Q

Resin injection or potted repairs are only performed on non-structural parts (T or F)

A

T

124
Q

What is the preferred type of repair

A

Permanent

125
Q

What procedures should a surface preparation involve

A
  • Thorough solvent degreasing
  • water break test
126
Q

What fasteners are pre-cured patch installed with to cover holes or deep scratches

A

Blind fasteners

127
Q

What are the 2 ways that a pre-cured patch can be secured

A
  • pre-applied adhesive
  • mechanical (metal) blind fasteners
128
Q

What is the problem with using fasteners on a pre cured patch

A
  • can cause damage to honeycomb core and lead to delamination
129
Q

If a honeycomb sandwich structure was damaged more than 2.5cm (1 inch) what can be used

A

Honeycomb plug

130
Q

How can you restore scratches

A
  • polishing, buffing, or even sanding
131
Q

Transparent plastics must never be sanded unless absolutely necessary (T or F)

A

T

132
Q

What does solid wood refer to on aircraft construction

A

Beams or spars

133
Q

What is plywood

A

Made of odd number of thin plies with each grain of each layer placed at 90*

134
Q

What temperature must fabric coverings be stored at?

A

20*c

135
Q

Seyboth/Maule punch tester are only designed for what covered aircraft

A
  • cotton and linen

M6 Resit (10 decks)

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