6.3 Composites Flashcards
(116 cards)
1
Q
what is a composite
A
2 or more materials that are combined to form a much stronger structure
2
Q
what are the 2 elements of a composite
A
matrix (resin)
reinforcing material (fabric)
3
Q
what are the most common used firbers used in aviation industry
A
fiberglass
aramid
carbon fibre
boron
ceramic
4
Q
what are the 2 types of fibreglass (think of mercedes)
A
e glass
s glass
5
Q
what is aramid
A
kevlar
6
Q
disadvantage of carbon fibre
A
corrosive when bonded to aluminium
7
Q
where is ceramic fibres used
A
high temperature applications (retains its strength up to 1200c)
8
Q
what direction does warp run
A
length of the fabric
9
Q
what direction does the weft/fill
A
perpendicular to the warp (weft to right)
10
Q
what direction is selvedge edge
A
parallel to warp threads
11
Q
what direction is bias
A
diagonal to warp
12
Q
what are mats
A
chopped fibres, compressed together
13
Q
what are the types of fabric weave
A
plain, twill, satin
14
Q
what weave is often used for repairs
A
satin weave
15
Q
what are the types of plastic
A
thermoset
thermoplastic
16
Q
what are thermoplastic resins
A
use a heat to form the part into desired shape, shape not always permanent
reversible process
17
Q
what are thermos set resisn
A
cured by heat, catalyst
once used and cured, cant be converted back to og state
18
Q
what type of resin is epoxy (thermoset or thermoplastic)
A
thermoset
19
Q
will the resin in pre-preg cure if not kept in cold storage
A
yes
20
Q
what is the procedure for opening pre-preg bags
A
bags must be opened in controlled environment, not opened until the material has reached room temp. bags must be resealed and returned to freezer. time out of freezer must be recorded
21
Q
what are the 2 main ways of constructing a fibre-reinforced composite
A
laminated composites
sandwich composites
22
Q
what is a laminated composite
A
2 or more layers of reinforcing material bonded together and embedded in a resin matrix
23
Q
what is a sandwich composite
A
when the core is bonded between two fibreglass sheets
24
Q
what is the main advantage of sandwich composites over laminated
A
extremely high strength to weight ratio
25
how many times stronger is a sandwich composite over a laminated composite
at least 10x stronger
weight is 6x more
26
what are some typical applications of sandwich composites
flying control surfaces, wing-to-body fairings, helicopter rotor blades
27
what are the 2 most common types of core material used in sandwich composite
honeycomb and foam
28
what are the two forms of transparent plastics
monolithic
laminated
29
how are thermoplastics marked
heated die
30
how are thermoset plastics marked
vibro etching
white paint and marking ink
31
how is transparent plastic marked
apply to metal portion if its attached to metal
if any markings must be applied, mark the inside of the panel by means of mild sandblasting and stencil
labels must not be stuck directly to the material
32
what is difference between adhesives and resins
resins used for laminating are thinner
adhesives are used for bonding two parts together
33
where does detection of defects within composite materials start
at the manufacturing process
34
why is too much resin an issue
added weight
35
how can delaminations form
from matrix cracks or impact
36
what is applied to composited to protect from UV
top coating
special UV primers and paints
37
what is the most common technique to detect delamination
coin tapping
38
what sound indicates a well bonded structure using coin tap test
clear, sharp, ringing sound
39
whats the best method to detect internal delaminations
ultrasonic inspection
40
how does thermograph inspection works
surface is heated, mapping the temperature.
defect free areas conduct heat more efficiently than areas with defects
41
what material is thermal methods most effective on
thin laminates or for defects near the surface
42
can dye penetrants be used on composite
no (unless specified by manufacturor)
43
what is used to detect water in sandwich honeycomb strtuctures
moisture detector (often used in nose radomes)
44
what are the 3 classifications of damage
negligible
repairable
non repairable
45
where is cosmetic defects found
outer surface skin
46
what is the most common cause of impact damage
careless handling during ground ops
47
what is BVID
barely visible impact damage
48
what is delamination
separation of fabric layers of material in a laminate
49
what causes delamination
impacts
moisture
lightning strikes
50
what is disbonds
separation of composite material from another material to which it has been bonded to
51
what is core disbond
separation between skin and core of composite
52
what causes disbond
poor adhesion
service loading
impact damage
53
how can water cause disbond
freezing during flight
54
how can holes occur
impact damage
over torquing
fasterner pull through
holes drilled in wrong location
lightning strike
55
what are the 5 types of composite repairs
pre-cured
potted
resin injection
laminate repair (one surface)
laminate repair (through part)
56
what are temporary repairs
bolted and bonded surface patches due to strength characteristics and aerodynamic smoothness
57
what is a permanent composite repair
removing damaged skin and replacing it with new repair plies
58
why is surface preparation important
significantly affects long term environmental durability
59
what test is used to verify surface cleanliness
water break test
60
what is an issue with using mechanical blind fastener
casue damage to honeycomb core and lead to delamination
61
what are potted repairs used for
smaller holes and scratches
eg bird strike or mechanical damage
62
what is potted repair
filler
63
what is the downside to potted repair
dont provide same structural strength
adds weight
decrease flexibility
64
what is the max size for potted repair
damage up to 1 inch 2.5 cm
65
how can minor delamination be repaired
injecting a potting compound, resin mixture
66
what is laminate repair
removing and replacing damaged laminate piles
67
what is most common types of honeycomb sandwich structure repairs
puncture repair
68
what are the major types of plastic failure
environmental
thermal
chemical
mechanical
69
are cracks in plastic repairable?
no it is rendered beyond repair
70
how to prevent cracks from spreading
stop drilling
71
what design did early wooden aircraft have
truss type wing and fuselage with fabric covering
72
in a truss type wing, which members in the wing are the spars?
lengthwise members
73
how is the truss held together
high strength solid steel wires
74
what are antidrag wires
attach rear spar inboard and go to front spar outboard
75
what is box spar
box structure is built between the spars, to carry bending and torsional loads
76
what is the most common wood used
sitka spruce
77
how is aviation wood usually cut
quarter sawn to reduce shrinkage
77
what is the maximum grain count for soft wood
six rings per inch
78
how can you finish repaired ribs, spars, interior of plywood skin and other internal members
by applying one thinned coat of varnish or acceptable finish
followed by two full coats
79
how much strength does wood lose at 50c
25%
80
how can bolt holes lead to decay or splitting
variations in moisture content around bolt holes
entry point for moisture
81
how can you seal bolt holes
application of varnish or acceptable sealer
must dry or cure thoroughly
82
how is wood quality assessed
how straight the grain is
the number of knots
how many pitch pockets
splits
83
what type of knots is not allowed in aircraft
spike knot
84
what is a spike knot
cut parralel to branch
85
what is a pitch pocket
opening in wood
86
when is a pitch pocket acceptable
in the middle of the beam
87
what is compression wood
when tree grows to one side
88
what is compression failure
when tree falls and lands across a log or uneven ground
89
what is a split in wood
runs lengthwise
90
what is a check
a crack in the wood that runs across the rings of a board
91
what is a shake
crack or separation of the board, occurs when 2 annual rings separate
92
how is decay caused
fungi
93
how can decay be prevented in wood
proper seasoning and storage
94
how to prevent dry rot
use kiln dried wood with a moisture content of 20% or less
use good surface finish like varnish or paint to protect the paint
95
how is casein glue made
milk
96
is casein glue used in aviation
no its bad and incompatible with modern glues, deteriorates with moisture
97
is resin glue used in aviation
no, it is susceptible to moisture
98
what is the most common type of glue in aviation
resorcinol glue
two part glue
synthetic
most water resistant
99
100
should you use sandpaper to smooth the surface of the wood you are glueing
no
101
what is the glue test sample
fractured wood must show atleast 75% of wood fibres
102
what device is best to cut fabric
pinking shears
103
what is dope
coating for fabrics, helps tighten, airtight, weatherproof.
104
what is a drawback for nitric dope
extremely flamable
105
is cotton a good fabric for aircraft
no
short service life
mildew, uv sensitive
not considered cost effective
106
what is polyester susceptible to
uv
can be prevented with coatings
107
where is glass fibre applied to
mainplane and tailplane in a spanwise direction
108
in what conditions should fabric be stored in
20c
dry
clean
out of direct sunlight
109
what are the 3 main common inspection panels
wood frames
zip panels
spring panels
110
are piercing fabric testing devices allowed
no
used at discretion of the engineer to form an opinion
111
what are the 2 types of fabric tester
maule
seyboth
112
are seyboth and maule fabric strength testers allowed on polyester
no
only allowed for cotton and linen
113
what stich is used for repairing cuts or tears
herringbone stitch
114
what is the selvage edge of a fabric
tightly woven edge that prevents fabric from unravelling
115
