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M6 > Composite And Non Metallic > Flashcards

Composite And Non Metallic Flashcards

1
Q

What is a composite material

A

Two or more materials joined together to make a strong structure

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2
Q

What are the advantages of composites materials

A
  • High strength-to-weight ratio
  • Reduction of parts and fasteners
  • Reduction of wear
  • Corrosion resistance
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3
Q

What are the disadvantages of composite

A

Generally expensive

Not easy to repair

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4
Q

What is nomex

A

very high thermal stability and temperature and flame resistance
Manufactured as a fibre
Gives major strength when combined with a matrix

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5
Q

What is nomex used for

A

Flame proof clothing

Primary flight controls

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6
Q

What is the relationship between nomex and Kevlar

A

Contrast chemical isomer

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7
Q

What is fibre glass

A

Made of Sillica glass spun into cloth
Weights more and has less strength than other fibers
Low cost

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8
Q

What are the 2 types of fibre glass

A
  • E-glass highly resistant to electricity

* S-glass very high tensile strength

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9
Q

What are the characteristics of fibre glass

A

◦ Low density (2.1 g/cm3)
◦ High Strength
◦ Hight fracture toughness
◦ Circular cross-section and smooth surface
◦ Good ‘wet out’
◦ The fibre does not absorb water/humidity
◦ The fibre is not ductile (ceramic properties)
◦ For sanding, aluminium-oxide or silicon-carbide sand paper can be used. Silicon-carbide will last longer than aluminium-oxid

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10
Q

What are the characteristics of aramid fibre

A 
◦ Low Density (1.45 g.cm3)
◦ High tensile strength
◦ Heat resistance up to 260°C
◦ Non-flammable and non-fusible
◦ Good chemical resistance
◦ Very good resistance against abrasion
◦ High toughness
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11
Q

What is aramid fibre

A

Yellow colour

Repaired with fibre glass

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12
Q

What is aramid used for

A

Rotor blades
Bullet proff vests
Use for leading edges

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13
Q

What is kevar

A

Man made

Organic fibre

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14
Q

What is Kevlar used for

A

Aircraft panels
Belts for radial Tyree
Bullet proff vests

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15
Q

What are the advantages of Kevlar

A

High tensile strength

Flexible

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16
Q

What are the disadvantages of kevlar

A

Absorbs up to 8% moisture
Poor compressive properties
Can’t be used to UV light
Difficult to cut

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17
Q

What are the advantages of carbon fibre

A 
High strength 
High stiffness
Low density 
Light weight 
High temperature resistance
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18
Q

What are the disadvantages of carbon fibre

A

Electively conductive
Can only the cut with air tools
Expensive

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19
Q

What is the relationship between Kevlar and graphite

A

Graphite is stronger in compressive strength than Kevlar, however, it is more brittle than Kevlar.

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20
Q

What happens with graphite is bonded with aluminium

A

Will become corrosive

Very course

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21
Q

What is the warp

A

Runs along length of fabric

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22
Q

What is the weft/fill

A

Runs perpendicular to the warp fibres.

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23
Q

What is the bias

A

The bias runs at 45° to the warp threads

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24
Q

What is the selvage edge

A

Runs parallel to the warp

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25
Q

What is a mat fabric

A

consist of chopped fibres that offer little strength compared with unidirectional or bi-directional threads.

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26
Q

What is a unidirectional fibre

A

Unidirectional fibres are ones in which the major fibres run in the direction of the warp

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27
Q

What is a bi-directional fibre

A

Bi-directional fabric calls for the fibres to run in two or more different directions

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28
Q

What properties do a matrix materials

A

good stress-distribution, heat-resistant, chemical-resistant and durability properties.

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29
Q

What is a thermo plastic

A

Can only with stand heat up to 750
Not permanent
Acrylic

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30
Q

What is a therm set

A

Thermosets use heat to form and set the shape permanently. The plastic, once formed, cannot be reformed even if it is heated.

Bakelite

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31
Q

What is pregreg

A

Pre impregnated fabrics
With a resin
Stored in a freezer to prevent curing

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32
Q

What is sandwich construction

A

When a core is bonded between 2 thin faces sheets

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33
Q

What is honey comb

A

Good strength to weight ratio

Nomax paper

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34
Q

What are the 2 honey comb fabrication methods

A
  1. Corrugationprocess:Materialwhichcanbeconvertedusingthisprocess include metals, plastics, plastic reinforced glass and paper.
  2. Expansionprocess:Inthisprocess,allbondsaremadesimultaneously(the corrugation process is essentially a one-layer-at-a-time operation).
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35
Q

What are methods use to dissipate the electraal change from composite

A
  • Flame spray
  • Bonding jumpers
  • Aluminium wires woven into the top layer
  • Thin aluminium foils bonded to the top layers hat
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36
Q

What is the MSDS

A

Materials safety data sheet

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37
Q

What will there be on MSDS

A
  • Health precautions
  • Flammability of the material
  • Ventilation requirements
  • Information for health professionals in the event of an accident
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38
Q

What is polymerisation

A

Carried out in the presence of a catalyst
Monomers becoming polymers
Chemical reaction
No waste product

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39
Q

What is polycondensation

A

chemical reaction between two similar or dissimilar basic units which have at least two functional groups.
Waste product of water
Bakelite and polyester

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40
Q

What is poly addition

A

two different types of molecules when reactive groups are brought together. No by-products are produced

Polyurethanes
Epoxies

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41
Q

What is an adhesive

A

Bonds 2 or more surface together

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42
Q

What do we use adhesives

A

economical; they distribute the stress at the bonding point, eliminate the need for fasteners and are moisture and corrosion-resistant.

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43
Q

What is the effective ness of a adhesive dependent on

A
  • Resistance to slippage and shrinkage
  • Malleability
  • Cohesive strength
  • Surface tension, which determines how far the adhesive penetrates the tiny depressions in the bonding surfaces.
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44
Q

What is a thermosetting adhesive

A

Used for bonding metallic parts of aircraft and space vehicles

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45
Q

What is a Thermoplastic resins,

A

which can be softened by heating, are used for bonding wood, glass, rubber, metal and paper products

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46
Q

What is a aerosil

A

white powder, which is a product of combustion. Aerosil is used as a thixotropic agent

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47
Q

What is a elastrometric adhesive

A

Used for joining dis similar metals with out galvanic crosion

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48
Q

What is a contact adhesive

A

Atmospheric pressure will press two solids together if there is no air between the two plane parallel surfaces

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49
Q

What is a solvent adhesive

A

Solvent adhesives contain plastics or resins dissolved in a solvent. The solvent has to evaporate to cure the adhesive

50
Q

What is a dispersion adhesive

A

Dispersion adhesives contain resins dissolved in a water solution, such as wood glue or wood paste.

51
Q

What is a resin adhesive

A

Resin adhesives cure by chemical reaction. They contain two or more components.

52
Q

What is a film adhesive

A

Similar to pre preg
Metal to Metal
Kepted in freezer m

53
Q

What is a foaming adhesive

A

A foaming adhesive film is an adhesive in sheet form which expands during the curing cycle to fill gaps and adhere strongly to all parts of the structure with which it comes into contact
Kept in freezer

54
Q

What is a plastic foam

A

Plastic foams are produced with either ”closed” or ”open” (interconnected) pores and as either preformed rigid sheets or as fluids for injection into cavities.

55
Q

What is a thixotripic agents

A

Thinking agent

56
Q

What are the 2 types of thixotropic agents

A

Aerosil

Micro bollon

57
Q

What is a micro balloon

A

Phenolic balls
Gently folded in
Trowled in time surface

58
Q

Mixing resins

A

Wax free container
3 to 5 minutes
Resin based stored in freezer

59
Q

What is a thermosetting resin

A

Epoxy resins are used for external components due to their good mechanical properties.
Phenolic resins are used for cabin furnishing due to their fire resistance and low toxicity.
Mixed with specific hardened and cured

60
Q

What is a thermo plastic resin

A

When heated, thermoplastic resin becomes a plastic. After cooling, the resin sets and hardens in a given form. Hardening is reversible. Thermoplastic resins are very seldom used on composite structures.

61
Q

What is a good polymer resin

A
  • It must have the correct mechanical properties.
  • It must coat every single fibre and bond well to them.
  • It must be fairly easy to use.
62
Q

What is a polymer resin

A

Polymers are combined with the fibres by melting or by using a liquid polymer (resin) that can be hardened (cured).

63
Q

Polyester Resin

A

typically used with glass fibre to form a strong durable material.

64
Q

Epoxy resin

A

thermosetting resin that provides excellent adhesive strength and can be used for glueing metals together.

65
Q

Vinyl Ester resins

A

are tough resins that have a high resistance to corrosion even in the presence of fuel. This makes them extremely useful for repairing fuel tank liners.

66
Q

Phenolic resin

A

used extensively inside aircraft due to good resistance to smoke generation in fires.

67
Q

What should you never mix together

A

Catalyst and a accelerator

68
Q

What are epoxy resins

A

Expensive
Viscous liquids
Mechanical properties

69
Q

What happens if too much hardener is added

A
  • Unreacted resin in the final cured resin

* Unreacted hardener in the final cured resin

70
Q

What are the disadvantages of epoxies

A

Toxicity
Low pot and shelf life
High cost

71
Q

Epoxy resin characteristics

A 
High adhesion 
Cohesive strength 
100% solid 
Low shrinkage 
Resistance to moisture and solvents
72
Q

What is a good surface wetting

A
  • Removal of surface contamination
  • Viscosity reduction through application of heat
  • Viscosity reduction by solvent or diluent addition
  • Time
  • Pressure
73
Q

What is mechanical booking

A

Must penatrate into cavities before curing other wise trapped air will reduce the strength of the joint

74
Q

What is surface wetting

A

Water drop test

75
Q

What are the pre treatments for bonding

A
  • Degrease only
  • Degrease, abrade and remove loose particles
  • Degrease and chemically pre-treat
76
Q

What is the first thing done when damage is done

A

A complete investigation into damages area
SRM
52-57

77
Q

Damage detection

A

Scheduled inspection

Unscheduled inspection

78
Q

Damage evaluation

A

Of the type
Extent
And importance

79
Q

What are the acceptance levels

A
  • Allowable
  • Repairable
  • Not repairable
80
Q

What are the 2 damage classification

A

Skin perforated damage

Skin not perforated damage

81
Q

What is Skin perforated damage

A
  • Lightning strike
  • Holes
  • Impact by foreign object, requiring investigation for delamination moisture contamination
82
Q

What is skin not performates damage

A
  • Abrasion
  • Scratches
  • Gouges
  • Nicks
  • Debonding
  • Delamination
  • Dents
83
Q

What is delamination

A

Reinforcing layers to separate from each other in the matrix m

84
Q

What is Barely Visible Impact Damage (BVID)

A

Lower velocity impact

Outer skin appears in damaged

85
Q

What is debonding

A

when two materials stop adhering to each other

86
Q

What testing methods used for BVID

A

Tap testing
Ultrasonic
X-rays

87
Q

What is abrasion

A

damage to a surface caused by scuffing, rubbing or scraping of the component.

88
Q

Lightening strike

A

Damage on carbon fibre structures will usually be less significant (spots, small holes, or charring).

89
Q

What is erosion

A

When moisture penetrates into composite

Leading edge surface

90
Q

Water absorption

A

Any moisture detected must be removed
Effects the resin
Reduces performance
Increases weight

91
Q

Chemical degradation

A

Chemical degradation principally affects the resin and is generally due to accidental contact with aggressive chemical liquids or products. If chemical degradation is detected, the whole contaminated area must be repaired.

92
Q

Dent / depression

A

A dent or depression is a deformity in the thickness of an area. It may be caused by impact. This type of defect requires further NDT (Non Destructive Testing) to detect delamination or debonding

93
Q

What is NDI

A

Non destructive testing

94
Q

Tap testing

A 
Widely used as it is quick 
Detects debonding 
Tapping surface lightly
Flat sound unacceptable 
Subjected to operator
95
Q

Visual or optical inspection

A

Dosent detect interval flaws

For fibre glass a light is shined through colour change when delamated

96
Q

Holography

A

rapid assessment of flaws in surfaces of composite structures.
Optical holography is extremely sensitive in measuring small surface defects.

The part to be inspected is stressed by the application of heat, a static load or vibration to bring out the effect of the flaw on the surface displacement

97
Q

Ultrasound

A

Locates internal defects

Inexpensive

98
Q

Radiography

A

X-ray inspection technique is widely used for quick and low-cost inspection of composite structures. X-ray equipment can be adapted to handle small parts up to relatively large parts.

A radiograph is like a shadow picture; the darker regions on the film represent the more penetrable parts of the test specimen and the lighter regions are more opaque to the radiation.

99
Q

Repair types

A
  • Temporary repairs
  • Permanent cosmetic repairs
  • Permanent structural repairs
100
Q

Preparation before repair

A

Surface protection removal
Clean and degrease area
Drying of area

101
Q

Removal of surface protection

A

Mechanical methods only

102
Q

What is scarfing

A

Removing a damaged composite material 1 later at a time

Removing a layer reveals 1/2 inch of the layer below

103
Q

What is a wet lay-up

A

Wet lay-up consists of applying several layers of fabric material impregnated with resin onto the repair surface, in order to restore the damaged skin.

104
Q

Pot life

A

(the amount of time you have to work with the resins

105
Q

Shelf life

A

The shelf life is the time which the product is still good in an unopened container and varies from product to product.

106
Q

Resin rich

A

If too much resin is used, the part is called resin rich. This is undesirable, as it affects the strength of the composite by making the part brittle and adds extra weight (negating the reason for using composites in the first place).

107
Q

Resin starved

A

If too little resin is used in the lay-up, it is described as being resin starved. This is undesirable as there is insufficient resin to successfully transfer stresses to the fibres

108
Q

Why is vacuum bagging used

A
  • To use atmospheric pressure to consolidate the layers in the laminated repair
  • To remove trapped air and gases produced during curing
  • To hold heater blankets, thermocouples and other materials in place during the curing cycle
  • To produce the desired surface finish on the repair
109
Q

What are the vacuum bagging principal

A
  1. Theairandgasesinsideavacuumbagmusthaveaneasypathtothe vacuum pump over the entire repair surface.
  2. Theamountofresinlostfromtherepairpliesmustbekepttoaminimum. Additionally, it is necessary to ensure that none of the bagging materials adhere to the repair and that the heater blanket is protected from resin contamination.
110
Q

Perforated parting film

A

This is a thin, non-stick film placed directly on the surface of the repair to prevent the bagging materials sticking to the repair surface. The film is perforated with small holes to allow air and gases to escape from the repair piles

111
Q

Peel ply

A

This is a thin, woven, nylon or polyester fabric which has a non-stick coating. It can be used instead of, or underneath, a perforated parting film.
Its main effect is on the surface finish of the repair.

112
Q

What are disadvantages of peel ply

A
  • It absorbs some resin, and may lead to a resin-starved repair.
  • It may contaminate the repair surface with its non-stick coating.
113
Q

Bleeder cloth

A

The function of this layer is to provide an easy path for air to escape and to absorb any resin which comes through the holes in the perforated parting film.

114
Q

Non perforated parting film

A

This is placed on top of the bleeder fabric to prevent resin soaking through onto the other bagging materials and the heater blanket.

115
Q

Breather fabric

A

This is a thick, porous, non-woven material and is used over the entire repair surface to allow the air and gases to escape easily

116
Q

Caul plate

A
  • To help even-out the temperature over the entire repair
  • To help even-out the pressure over the whole repair
  • To improve the flatness of the surface of the repair
117
Q

Heater blanket

A

The heater blanket is a silicone rubber pad which contains an electrical heating element. It is used to control the temperature of the repair during the warm-up, cure and cool-down stages of the repair. It is flexible and will bend to gentle curves. Heater blankets can be used for cures up to 350°F (175

118
Q

Insulation

A

Insulation in the form of breather fabric or glass cloth is normally placed on top of the heater blanket to reduce heat loss and to minimise the effects of draughts on the repair.

119
Q

Bagging film

A

This is a nylon film which is sealed over the repair materials so that a vacuum can be applied. It is available in a variety of temperature / elongation resistant types. The higher temperature-resistant films normally stretch less.

120
Q

Bag seating tape

A

This material is a high temperature mastic type of tape and is used to seal the vacuum bag to the surface of the item under repair. It is available in a number of temperature ranges.

121
Q

Thermo couples

A

positioned under heating mats in order to accurately monitor the repair temperature.
J type

122
Q

Flash breaker tape

A

It will not be affected by high temperatures. It is the only type of tape which should be used on the surface of the heater blanket.

M6 (13 decks)

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