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Kemble > M6.3 Composites > Flashcards

M6.3 Composites Flashcards

1
Q

What is a composite

A

Two or more materials combined to make it stronger than they would be on their own

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2
Q

What is the role of the matrix and what does it do?

A

. Bonds to fibre
. Transfers stress
. Adds strength to fibre

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3
Q

What are the parts of a 2 part matrix mix?

A

Resin, hardener

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4
Q

What are the 2 main elements that make up a composite (plus sometimes 3rd)

A

Matrix (bonding)
Reinforcing material (fabric)
Core (sandwich construction)

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5
Q

What are the 2 categories of a matrix?

A

. Thermoplastics
. Thermoset

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6
Q

What’s a thermoplastic?

A

Non permanent change and can be reversed

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7
Q

What are a few advantages of composites

A

Longer service life than metals
Higher corrosion resistance
High strength to weight ratio
Fibre to fibre transfer of stress

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8
Q

What is a Thermoset?

A

Permanent change and cannot be reversed

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9
Q

What’s a thermoset?

A

Permanent change and cannot be reversed

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10
Q

What are some disadvantages of composites

A

Inspections difficult to conduct
High cost production and repair
Lack of knowledge
Often toxic and hazardous

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11
Q

Describe epoxy resin?

A

. Most common
. Thermoset
. Bond almost any materials together

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12
Q

What is fibreglass

A

Small strands of silica glass and the spun into woven cloths

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13
Q

What are the two types of fibreglass

A

E glass
S glass

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14
Q

What are some advantages of fibreglass

A

Low density
Hugh strength
Good wet out💦💦💦💦💦
Does not absorb water
Not ductile

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15
Q

What is pre-preg? 😩🧐😉

A

. Controlled amount of resin added to a material to prevent errors

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16
Q

What are the properties of Aramid (Kevlar)

A

Yellow colour
Lightweight
Can repair with fibreglass

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17
Q

What is Kevlar used for

A

Belts for radial tyres
Bullet proof vests

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18
Q

What are the disadvantages of Kevlar

A

Very difficult to cut
Special cutters needed
Poor compressive properties
UV sensitive (turns brown)

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19
Q

What is CFRP

A

Carbon fibre (black graphite)

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20
Q

Where do you store pre-preg materials and how do you monitor it?

A

In a freezer and calculate time out of freezer with freezer log

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21
Q

What are some advantages of Carbon Fibre

A

Very strong and stiff
High resistance to temperatures
Stronger than Kevlar but more brittle

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22
Q

Disadvantages of pre-preg 😳🥵🤪😱🫠🥱🫶🏿

A

. Short life span
. Very expensive

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23
Q

What composite is corrosive with aluminium

A

Carbon fibre

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24
Q

What is carbon fibre used for on an aircraft

A

Primary structures
Ribs
Floor beams

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25
Q

What are some disadvantages of carbon fibre

A

Wears out tooling
Very conductive

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26
Q

Why is boron not commonly used

A

Expensive
Hazardous

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27
Q

What is laminate made of?

A

2 or more layers of reinforcing material bonded together with matrix

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28
Q

When would you use ceramic composites

A

For high temperature applications

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29
Q

What is a sandwich (not the food kind Sean 💀)?

A

. Core bonded between 2 thin fibreglass sheets
. High strength:weight

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30
Q

How much stronger is sandwich than laminate?

A

10x

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31
Q

What is the warp

A

Runs along the length of the fabric as it comes off a roll (0^)

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32
Q

What is the weft

A

Runs perpendicular to the warp (90^)

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33
Q

What is the Bias

A

Runs 45^ to warp

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34
Q

What is the selvedge edge

A

Prevents material from fraying or unravelling. Tightly woven edges run parallel to warp threads

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35
Q

What are examples of things a sealant seals?

A

Fuel tanks, skin joints, structures

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36
Q

What are the 2 core materials?

A

Honeycomb, Foam

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37
Q

What are the 4 styles of fabric

A

Unidirectional
Bidirectional fibre
Mats
Quasi-isotropic

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38
Q

What is unidirectional fabric style

A

Fibres run in single direction of the warp

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39
Q

What is bidirectional fibre style

A

Fibres run in 2 or more different directions

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40
Q

What are the advantages of plastic?

A

. Lightweight
. Cheap
. Corrosion resistant
. Durable
. Impact resistance
. Chemical resistance

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41
Q

What is mats style of fabric

A

Chopped fibres, offers little strength

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42
Q

What are the advantages of PTFE?

A

. Electrical insulator
. Low flammability
. Tear resistant

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43
Q

What is quasi-isotropic fabric style

A

Lay ups stacked in 90^, 45^, 90^ sequence
Or 0^, -60^, 60^
Provides strength and stiffness in all directions

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44
Q

What are the 3 types of fabric weave

A

Plane
Twill
Satin

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45
Q

What is plain weave

A

Simplest form
Very stable
Difficult to cover complex shapes, won’t drape
Lowest mechanical properties

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46
Q

What is twill weave

A

Good wet out and cover properties
Flatter and offers superior mechanical properties

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47
Q

How do you identify a thermoplastic?

A

. Heated dies

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48
Q

How do you identify thermosetting plastics?

A

White paint or ink

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49
Q

What is satin weave

A

Modified twill with fewer intersections
Flat, covers well, good wet out
Often used for repairs
However,
Difficult to handle

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50
Q

How do you identify transparent plastics?

A

Mark on metal bit or sand blasting

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51
Q

Where do you store film adhesive to slow resins cure rate

A

A freezer

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52
Q

What is a one part sealants?

A

Ready for application as packaged

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53
Q

What do two part sealant require in packaging?

A

Require separate packaging to prevent curing prior to application

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54
Q

What happens to film adhesive at room temp?

A

The resin starts to cure

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55
Q

What happens to foam adhesive under heating

A

Expands into crevices

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56
Q

What are foam adhesives used for?

A

Bond new honeycomb core segments to existing cores

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57
Q

What do in service defects include?

A

Impact strength
Environmental degradation
Cracks from load overload
Fatigue

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58
Q

What are the three categories of damage to composites

A

Negligible
Repairable
Non repairable

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59
Q

What are cosmetic defects

A

Defects on the outer surface, does not involve damage to structural reinforcing fibres

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60
Q

What does BVID mean

A

Barley visible impact damage - due to being difficult to see and deftest

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61
Q

What is delamination

A

Separation of the fabric layers of on a laminate
Due to impact, moisture or lightening strikes

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62
Q

What do erosion prone areas require?

A

Coatings and protection

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63
Q

When would a dye penetrant be used?

A

When called upon by manufacturer

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64
Q

What does a visual inspection consist of looking for?

A

Scorching
Stains
Dents
Penetration
Chips

65
Q

What is disbonding

A

separation of the composite material from another material to which it has been bonded to
separation between the skin and core of a composite sandwich structure is called core disbond

Caused by poor adhesion impact damage

66
Q

How can cracks be detected

A

Visually or by NDT
Thorough inspection

67
Q

How can you inspection if there has been water ingress ion

A

Weight gain
Contamination of bond
Expansion/contraction (Therese thaw)

68
Q

How does hole damage arise

A

Impact, over torquing, lightning strike pin holes

69
Q

Can x rays detect delamination

A

No

70
Q

What must be done in preparation to before bonding

A

Solvent Degreasing and de oiling

71
Q

How is a surface checked to see if it has been properly prepared before bonding is applied

A

A water break test it carried out (if beads then it’s been done incorrectly)

72
Q

What are the parts of a truss type wing?

A

Main and rear spar
Compression strut
Drag wires (drag and anti drag)

73
Q

What are the parts of a truss type wing?

A

Main and rear spar
Compression strut
Drag wires (drag and anti drag)

74
Q

How does the box spar help the wing?

A

Takes all of the torsional and bending load

75
Q

What are the types of wood that could be used for an aircraft structure?

A

. Solid wood
. Laminate wood
. Plywood
. High density wood

76
Q

What are the 3 preferred wood types for aircraft?

A

. Spruce
. Douglas Fir
. Noble Fir

77
Q

What are the 5 types of composite repairs

A

Pre cured patches
Potted
Resin injection
Laminate repair (one surface)
Laminate repair (through part)

78
Q

What’s the negatives of pre cured patches

A

Doesn’t provide the same aerodynamic properties

79
Q

What’s potted repairs

A

Where a small hole is filled with foam filler instead of having a core

80
Q

What do you asses in a wood inspection? (Pre plane built)

A

. Way it’s cut
. It’s grains
. Wood growth ring
. Grains slope

81
Q

What’s the negatives of potted repairs

A

They can be dangerous as they make it heavier

82
Q

What is solvent degreasing

A

Removes contaminates from surface, if not removed could effect bonding

83
Q

What causes wood to decomposed?

A

Moisture, temperature, sunlight

84
Q

What kind of hangars should wooden aircraft be stored in?

A

Well ventilated hangars, out of sunlight,

85
Q

What could be used to preserve wooden structure?

A

Chemical preservatives

86
Q

What is a water break test

A

To verify surface cleanliness

87
Q

What does interior finishing do?

A

Protect against moisture using coatings

88
Q

How’s resin injection carried and why is it carried out

A

Carried out when delamination occurs and it’s done by injecting the area with resin and clamped

89
Q

What is exterior finishing in wooden aircraft?

A

Weathering protection, smooth surface as needs to be aerodynamic

90
Q

What needs to happen before you make repairs to wooden structure?

A

. Degrease
. Remove sawdust
. Controlled temperature
. Seal bolt holes

91
Q

What MSDS stand for

A

Material safety data sheet

92
Q

What is a knot is wood?

A

. Where old branch grew
. Weakens wood

93
Q

What is a pitch pocket in wood?

A

. Small opening in wood , fill with resin

94
Q

What’s contained on the MSDS

A

PPE
ventilation
Fibre protection
Solvents safety
Material storage

95
Q

How is compression wood formed?

A

. Leans one side during growth
. Rings out of sync
. Makes wood weaker
. Falls on slope or another log
Can’t use on aircraft’s

96
Q

What is compression failure?

A

When a tree falls on uneven ground

97
Q

Describe stained wooden structure?

A

. Has stains caused by decay
. Reduces toughness/strength
. Cannot be used

98
Q

What’s happens if crazing isn’t detected

A

Can lead to cracking and failure

99
Q

What is dry rot and what’s it caused by?

A

. Caused by fungi
. Has minimum moisture

100
Q

Where should wooden structures be kept?

A

A well ventilated hangar

101
Q

What part of the wooden wing takes all of the structural loading

A

The spar

102
Q

How is the majority of wood damaged?

A

Moisture, temperatures, sunlight (UV)

103
Q

What is the main characteristic of resorcinol glue?

A

Most water resistant

104
Q

What separates the leading and trailing edge of the wing

A

Compression struts

105
Q

Where would you use a pre cured patch repair

A

a temporary repair can be performed to cover holes or deep scratches by using a pre-cured patch installed with blind fasteners
Yet, does not produce same structural strength as original

106
Q

How is wood testing done?

A

Test of joining technique

107
Q

What prevents the leading edge of a wooden wing from collapsing

A

The drag wire

108
Q

What things would you look for on the wood when you inspect it for damage?

A

Decay, splitting or cracks, bond failure, finish failure, stress damage

109
Q

What prevents the trailing edge from collapsing forward

A

Anti drag wire

110
Q

H

A
111
Q

What does the box spar do

A

Takes all bending and torsional load

112
Q

What wood is most commonly used for aircraft structure

A

Silka spruce

113
Q

How many screws and nails per spar

A

No more than 2

114
Q

Why should drain holes be kept clear

A

Because it can cause rotting of wood id not due to moisture being held in wind

115
Q

How is a wood test sample performed?

A

. Wood glued together put in vice
. Hit apart with device of some sort
. The fractured face must have at least 75% wood to show a good joint glued

116
Q

What size hole is a fabric patch repair used for

A

Up to 1 inch

117
Q

What’s the limit of age rings that can be in 1 inch

A

6

118
Q

What size hole for surface patched repair

A

Between 1 inch and 50inchs😏

119
Q

What is a potted repair

A

Used for smaller holes up to 2.5cm and scratches. Filler is used instead of a new core.
Restricted to honeycomb core sandwich structure

120
Q

What is a plug patch repair held in by?

A

Held in by a round or oval shaped ring called the doubler

121
Q

What area of the part is plug patch repair done on

A

Only skin repair, only for damage not involving the supporting structure

122
Q

What is the negative of nitrate dope

A

Extremely flammable

123
Q

What defects in wood can’t be used in aircraft structures

A

Spiked knots and compressed wood

124
Q

What is a resin injection used for

A

Minor internal delamination can be repaired by injecting a resin mix into delaminated area.
Have to check structural repair manual for limitations.

125
Q

What types of

A
126
Q

What is added to butyrate dopes to stop UV damage

A

Aluminium

127
Q

What does stained wood indicate

A

Indicates that rotting has occurred

128
Q

What are laminate repairs

A

Repairs damage on one side of the surface that does not penetrate the part.
Cut out the damage and replace with new material

129
Q

Before joint two pieces of wood what process must it go have gone through before hand

A

Must have been left in the same temp for previous 24 hrs so that it can gain the same moisture levels

130
Q

Can you do a laminate repair for damage that has gone through the part

A

Yes, can be repaired using a step cutting from both sides and meeting in the middle and the replaced.
Check AMM for limitations

131
Q

What does MSDS mean

A

Material safety data sheets

132
Q

What stitch is used to repair straight cut or tear

A

Ladder/baseball stitch (Herringbone stitch)

133
Q

When testing bonding techniques between two pieces of wood what percentage of fibres must be on the piece of wood

A

75%

134
Q

How is a good fit of a fabric achieved

A

Hot ironing

135
Q

How’s solid wood repaired

A

By splicing

136
Q

What is included within the MSDS requirements

A

PPE
Ventilation- proper ventilation, respirators provided
Fire protection- spark proof tools, eliminate fire hazards
Solvents Saftey
Material storage

137
Q

What are the two most common solvent used

A

MEK (carcinogen) and acetone

138
Q

Where should fabrics be stored?

A

At 20 degrees (68f) in dry clean condition away from direct sunlight

139
Q

What’s the restriction related to splicing solid wood

A

No more than 2 per spar

140
Q

What things would you look for in a fabric inspection?

A

Loose tape
Chafing under fairings
Brittleness
Tears

141
Q

What are the 5 types of plastic failure

A

Environmental failure
Chemical failure
Mechanical failure

142
Q

What’s used for wing rib repairs

A

Small sprite strips

143
Q

What are 3 commonly inspected panels

A

Wood frames
Zip panels
Spring panels

144
Q

What’s the restrictions for in which fabric patch repairs can be done.

A

Can’t be done on leading edge

145
Q

How is fabric attached to the wood

A

Using dope

146
Q

2 types of fabric testing devices

A

Seyboth punch tester- goes all the way through
Maule punch tester- doesn’t puncture , better as it doesn’t make hole

147
Q

What’s the negative of using dope

A

It’s very flammable

148
Q

When would darning be used?

A

Hole is no more than 50mm wide at any point (2inchs😏)

149
Q

What is crazing

A

Internal cracking, can’t be removed or fixed as it’s separation of the material.
If left then could become extensive deep crack.
Prevention is paramount

150
Q

What’s added to make dope less resistant to uv

A

Alluminium

151
Q

When would an insertion be used for repair?

A

Damage over 100m (4inch😉)

152
Q

When would an insertion be used for repair?

A

Damage over 100m (4inch😉)

153
Q

How are fabric wings inspected

A

Using inspection panels

154
Q

How can you get rid of scratches

A

Buffing or sanding
It is easier to prevent than remove
Refer to AMM for limitations

155
Q

What are the three panels installed in wings

A

Spring, wooden frames and zip panels

156
Q

What are the two tools used to measure tension of fabric

A

Seyboth and maule

157
Q

What does cracking cause and how can you prevent it from getting worse

A

Renders the plastic beyond repair.
Can be stopped drilled to prevent further damage.
Will require replacement at some point.
Refer to AMM

158
Q

Which one of the two devices that test tension are better

A

Maule is better and the seyboth punctures a hole in the fabric

Kemble (39 decks)

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