6.3 Aircraft Materials Composite Flashcards
(110 cards)
1
Q
Some modern aircraft have what percentage of composite structure?
A
50%
2
Q
What does the term composite mean?
A
Two or more materials combined to make one much stronger material.
3
Q
What is the simplest composite composed of?
A
Matrix- bonding
Reinforcing material
4
Q
What third material can sometimes be added?
A
A core material such as honeycomb
5
Q
What is the tensile strength of composite compared to steel or ally?
A
4-6x
6
Q
What is the primary load carrying element of composites?
A
The fibre
7
Q
What are some of the most common fibres used?
A
Fibreglass
Aramid
Carbon fibre
Boron
Ceramic
8
Q
Is fibreglass a conductor?
A
Yes
9
Q
What are the two most common types of fibreglass?
A
E glass
S glass
10
Q
What is E glass fibreglass?
A
Used for electrical applications due to its huge resistance to flow and is the most common fibreglass.
11
Q
What is S glass fibreglass?
A
High strength
12
Q
What does Aramid stand for?
A
Aromatic Polyamide Polymer
13
Q
What is aramid more widely known as?
A
Kevlar
14
Q
What are the two most common aramids used?
A
Kevlar 49 and Kevlar 29
15
Q
Where is aramid used to be a benefit?
A
Areas where impact resistance is req.
16
Q
What is the density of aramid?
A
1.35g/cm
17
Q
What is the heat resistance of aramid?
A
260 degrees c
18
Q
What is the negative of aramids?
A
They can absorb liquids
19
Q
What happens when aramid is exposed to UV?
A
It turns brown.
20
Q
What is the differences between aramid and carbon fibre?
A
CF has stronger compressive strength but is more brittle than aramid.
21
Q
To what metal is carbon fibre galvanic?
A
Aluminium, a sheet of fibreglass must be used to isolate them.
22
Q
How are boron fibres made?
A
Applying a small amount of vaporised boron onto thin tungsten or carbon wire.
23
Q
What is the most common use for boron?
A
Used to repair cracked aluminium parts and panels.
24
Q
Where are ceramic fibres used?
A
High temps up to 1200 degrees c
25
What is the warp?
Lengthwise threads
26
Is the fabric normally stronger in the warp or weft?
Warp
27
What is the weft?
Width
28
What is the selvedge edge?
Tightly woven edge that runs down the warp to prevent unravelling
29
What happens to the selvedge edge before the fabric is used?
It is removed
30
What is the bias?
The diagonal, facilitates manipulation of the fabric
31
What four different styles of lay up are used?
Unidirectional
Bidirectional
Quasi-isotropic
Mats
32
What are unidirectional fibres?
The major fibres run in the warp direction with only occasional traverse threads to hold it together.
33
What are some examples of unidirectional lay up?
Glass fibres
Carbon fibres
Aramid fibres
34
What are bidirectional fibres?
Where the threads run in two directions. Warp normally outnumbers the weft threads.
35
What is a quasi-isotropic lay up?
When the layers are at 45 degrees to the previous layer, such as carbon fibre.
36
What are some of the most common weaves?
Plain
Twill
Satin
37
What does twill weave provide?
Superior wet out
38
Why are polyester resins not suitable for any loads?
Too brittle
39
What is the modern resin matrix?
Epoxy
40
Resin matrix systems are a type of plastic, what two types are there?
Thermoplastic
Thermosetting
41
What is an example of thermoplastic parts?
Windshields and side windows
42
What is key about anything made in a thermosetting process?
It is irreversible.
43
Are epoxy resins thermosetting or thermolastics?
Thermosetting
44
When unmixed what is the shelf life of epoxy resin?
One year at 22 degrees c
45
What do prepreg fabrics help eliminate?
Error during mixing and application process
46
Although prepreg has lots of pros what are some of the cons?
Must be stored frozen
Full rolls must be purchased
More expensive
47
What are the two ways to construct fibre reinforced composite?
Laminate
Sandwich
48
What is an interply hybrid?
When two different fabrics are used in a laminate to combine their characteristics.
49
What is a sandwich construction?
When the core is bonded with two thin fibreglass sheets.
50
What is the benefit of sandwich construction?
It is approx 10 times stronger than laminate and only 6 times heavier
51
What are the two most common core materials?
Honeycomb and foam
52
What is honeycomb normally made from?
Aramid paper
53
Most honeycombs are hexagonal but what two other forms are available?
Flexi core and over expanded core
54
What are some foam cores made of?
Polystyrene
Polyvinyl Chloride
Polyurethane
55
What range of uses do plastics have?
Structural components to decorative trim to windows.
56
What is polyetherketone (PEEK)?
Semi-crystalline organic polymer
57
What are some of the characteristics of PEEK?
Superior mechanical and thermal properties
Creep resistance
Low flammability
58
What is the operating temp of PEEK?
Up to 232 degrees c
59
What is thermosetting polyimide used for?
Stand offs, and a variety of moulded parts
60
Where is PAI (polyamide-imide) used?
Aircraft thrust reverser assemblies due to its high mechanical strength which it keeps up to 260 degrees c
61
What two forms can transparent plastic be formed in?
Monolithic
Laminated
62
What is a monolithic plastic sheet?
Made in a single layer
63
What are clear laminated plastic sheets bonded with?
Layer of clear resin material.
64
How are thermoplastics marked?
Heated dyes
65
What is heated dye marking not suitable for?
Tubular sections
Celluloid and vinyl acetates
66
How are thermosetting plastics marked?
Vibro-etching (preferable)
White paint and marking ink
67
How are transparent plastics marked?
Ideally not at all.
68
What two forms are sealant available in?
One part
Two part to be mixed
69
What are some of the applications of sealant?
Fuel tanks
Skin joins
Aerodynamic smoothing
70
What is film adhesive?
It pre-blends the resin and catalyst on a film of plastic.
71
What are adhesive films used for?
Bond patches to a repair area.
72
What is another form of adhesive primarily used to bond foam to honeycomb?
Foaming adhesive, can also be used to permanently install fasteners.
73
Where is detection of defects in composite started?
Manufacturing process
74
How is a resin starved areas identified?
Fibres showing on the surface.
75
What can delaminations form?
Matrix cracks
76
What does the severity of delam depend on?
Dimensions
Number of delams at location
Location
Loads
77
Honeycomb structures have face sheets which are subject to three categories of defect, what are they?
Low resistance to impact
Liquid ingression
Erosion
78
Damage that goes unchecked to a honeycomb structure can lead to what?
Liquid ingress into the core
79
When a core has water ingress what is required before carrying out a repair?
Drying cycle to completely remove any moisture.
80
When a core has skydrol ingress what is required before carrying out a repair?
Complete removal of contaminated core as it cannot be dried.
81
What are some of the typical types of visual damage?
Scorch
Stain
Dent
Penetration
Abrade
Chip
82
How are internal defects inspected?
NDT
83
What is the most common test for detecting delam?
tap/coin testing
84
What four ultrasonic techniques are used?
Through transmission
Pulse echo
Ultrasonic bond
Phased Array
85
What is x-ray best at detecting?
Flaws parallel to the beams centreline.
86
As most composites are transparent to x-rays what is used?
Low energy rays
87
What is thermography most affective for?
Thin laminates or defects near the surface
88
Ife dye penetrant sits on composite too long what happens?
The fibres can absorb the dye.
89
How does a moisture meter work?
The meter measures the RF power loss caused by the presence of water.
90
What are the three damage classifications to composite?
Negligible
Repairable
Non-repairable
91
What is BVID?
Barely visible impact damage
92
What are the five basic types of composite repairs?
Pre-cured patches
Potted
Resin Injection
Laminate repair (one surface or through part)
93
What are bolted and bonded repairs?
Temporary
94
What are resin injection and potted repairs for?
Repair small holes or voids.
95
What steps are required to prepare a surface for repair?
Solvent degreasing
Water break test
96
What is the water break test?
A test to see what the surface tension of the water is.
97
How long must the water remain on the surface in a water break test?
30 seconds
98
What are the 8 basic steps when assessing damage for repair?
Find
Assess
Define SRM
Prepare
Lay up
Clean
Inspect
Document
99
How does a potted repair, repair a hole?
Filler is used instead of new core material.
100
What is the maximum size for a potted repair?
2.5cm
101
What are the two most common honeycomb repairs?
Puncture
Honeycomb core
102
If honeycomb damage is more than one inch, a potting repair can't be used, what can be done instead?
A honeycomb plug cut and bonded in place.
103
What are the two common solvents used to clean composite?
MEK
Acetone
104
What types of plastic wear are there?
Crack, degradation, distortion and aesthetic alteration.
105
What are the four types of plastic failure?
Environmental
Thermal
Chemical
Mechanical
106
What are the rules for cleaning an externally exposed surface?
Flush the surface with water and use a hand to remove all the dirt. Sponge with hot water and soap, dry.
107
What are the rules for cleaning an internal plastic surface?
Dust the surface, use a damp cloth and dry. Use approved plastic cleaner/polish.
108
What is crazing?
Small surface fissures, can lead to major cracking.
109
How can scratches be removed?
Buffing
Sanding
110
What can be done to cracks in plastic?
They can be stop drilled , but the component must still be replaced at next check.
