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M6 > Composite And Non Metallic > Flashcards

Composite And Non Metallic Flashcards

1
Q

Composite

A 
The combination of two or more materials to form a much stronger structure 
A matrix (Usually liquid)
A reinforcing material
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2
Q

Advantages and Disadvantages of Carbon Fibre

A

High strength to weight ratio
Corrosion resistance
Resistant to wear

Expensive
Not easy to repair
Requires trained staff

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3
Q

Reinforcing materials

A

Gives strength to the reinforcing component when combined with the matrix

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4
Q

Nomex

A

Manufactured only as a fibre

Flame and temperature resistant

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5
Q

Fibreglass

A 
Molten silica glass, spun together and woven into a cloth 
Low cost weighs the most 
Least strength 
E-Glass = Electrical resistance 
S-Glass = High tensile strength
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6
Q

Aramid

A

Yellow in colour
Good tensile strength
Heat resistant up to 1260 C
High toughness

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7
Q

Kevlar

A

Man made organic fibre
High tensile strength
Difficult to cut
Absorbs 8% moisture

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8
Q

Carbon fibre (CFRP)

A

High strength
Stiff
Low density
Electrical conductivity

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9
Q

Warp

A

Threads run along the length of the fabric

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10
Q

Weft/Fill

A

Runs perpendicular to warp fibres

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11
Q

Selvedge

A

Tightly woven edge runs parallel to warp edge

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12
Q

Bias

A

Runs 45 degrees to warp threads

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13
Q

Matrix Materials

A 
Good stress distribution
Heat resistant 
Chemical resistant 
Good durability 
Resins used as a matrix are two part systems
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14
Q

Thermoplastics

A

Use heat to form the part into a specified shape and this shape is not permanent

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15
Q

Thermoset

A

Once heated they form a permanent shape
Cannot be deformed
Most commonly used

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16
Q

Pre impregnated materials

A

A combination of a matrix and fibre reinforcement
Must be stored in a freezer at a temperature below 0 F
Many materials in aerospace are impregnated with Alan epoxy resin, cured at 250 F or 350 F

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17
Q

Honeycomb construction

A

This type of core material has the shape of natural honeycomb and has an excellent strength-to-weight ratio. Honeycomb materials can be constructed of aluminium, Kevlar, carbon, fibreglass, Nomex or steel. Nomex is a paper that has been impregnated with aramid and is very often used on so-called advanced composites.

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18
Q

Electrical Bonding

A

There are a lot of different methods used by manufacturers to dissipate the electrical charge on composite components:
• Flame spray
• Bonding jumpers
• Aluminium wires woven into the top layer
• Thin aluminium foils bonded to the top layer

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19
Q

Safety

A

All is listen in the MSDS
Wear correct PPE
No contact lenses

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20
Q

Polymerisation

A

Carried out in the presence of a catalyst
Creating a chemical reaction
Creates a monomer
No waste product

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21
Q

Polycondersation

A

Chemical reaction between two similar and dissimilar units

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22
Q

Polyaddition

A

Reduction of two different molecules
No by products
Hydrogen atoms migrate

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23
Q

Adhesives

A

An adhesive is a substance used to bond two or more surfaces together. Most adhesives form a bond by filling in the minute pits and fissures normally present even in very smooth surfaces. Adhesive bonds are economical; they distribute the stress at the bonding point, eliminate the need for fasteners and are moisture and corrosion-resistant.

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24
Q

Effectiveness of adhesives depend on

A

Resistance to slippage and shrinkage
Malleability
Cohesive strength
Surface tension

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25
Q

Synthetic adhesive

A

Used either alone or as modifiers of natural adhesives, perform better and have a greater range of application than the natural products. Most of them form polymers, which are huge molecules incorporating large numbers of simple molecules to form strong chains and nets that link surfaces in a firm bond.

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26
Q

Thermosetting adhesive

A

Bonding metallic parts of the aircraft

27
Q

Thermoplastic adhesives

A

Bonding woods, glass, rubber and paper

28
Q

Elastomeric adhesives

A

Join dissimilar metals without the hazard of producing galvanic corrosion.

29
Q

Contact adhesive

A

Pressure will press two solids together if there is no air between the two plane parallel surfaces.

30
Q

Solvent adhesive

A

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

31
Q

Dispersion adhesive

A

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

32
Q

Resin adhesive

A

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

33
Q

Film adhesive

A

They are used for bonding metal to metal, sandwich core to skin.

34
Q

Foaming adhesive film

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.

35
Q

Plastic foams adhesive

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.

36
Q

Thixotropic Agents

A

Micro balloons
Diameters = 10 - 300 microns
Forms a paste
Acts like a filler

37
Q

Most common resins

A

Polyester
Epoxy
Vinyl Ester
Phenolic

38
Q

Adhesion

A

Epoxies have high adhesion to metals, glass and ceramics. They can be formulated to give mixes of low viscosity with improved wetting, spreading and penetrating action.

39
Q

Cohesion

A

When the resin is properly cured, the cohesive strength within the glue line is so great (and adhesion of the epoxy to other materials so good) that failure under stress often occurs in one of the adherents rather than in the epoxy or at the interface

40
Q

100% Solids

A

Unlike phenolics and some other resinous adhesives, epoxies cure without releasing water or other condensation by-products. This makes it possible to bond epoxies at contact pressure only, or with no pressure at all.

41
Q

Low shrinkage

A

Epoxies cure with only a fraction of the shrinkage of vinyl-type adhesives such as polyesters and acrylics; consequently, less strain is build into the glue line and the bond is stronger.

42
Q

Epoxies resistance to moisture solvents

A

Epoxies are insensitive to moisture. Their resistance to solvents is also outstanding and accounts for their rapid advance in the coatings field. They are effective barriers to heat and electric current.

43
Q

Positive effects of surface wetting

A

Should always be kept clean
Viscosity reduction
Time
Pressure

44
Q

Negative effects of wetting

A

Finger prints
Incorrect glue
Low temperature

45
Q

Bonding pre-treatment

A

De grease
De grease, abrade and wipe
De grease and chemically pre-treat

46
Q

Composite damage investigation

A

Area
Extent
Type

47
Q

Levels of damage

A

Allowable
Repairable
Non-repairable

48
Q

Skin not perforated

A

Erosion/abrasion/scratches
Gouges/nicks/dents
Deboning/delimitation

49
Q

Skin perforated

A

Lighting strike

Holes/FOD impact

50
Q

Delimitation

A

Reinforcing materials spreading from each other in the matrix

51
Q

Deboning

A

Two materials stop adhering to each other

52
Q

BVID

A

The outer skin may be undamaged, however underneath the damage may be fatal

53
Q

Corrosion

A

Galvanic corrosion may occur when an aluminium alloy part is in direct contact with a carbon fibre surface in the presence of a corrosive environment.

54
Q

Erosion

A

Erosion could affect all the leading edge surfaces, especially when the initial surface protection system has been damaged. Erosion, when undetected or unrepaired, may generate composite deterioration. The component may be completely perforated and fluid ingress likely to occur. Restore the protection of the area and install additional protection if necessary.

55
Q

Water abrasion

A

Any detected moisture has to be removed to avoid further damage.
During any repair procedure, ensure that repair parts are completely dry,
in order to avoid any material delamination during heat application. Water ingress in sandwich structures is due to porosity of the skin. It reduces performance and increases the weight of the affected structure. Water absorption is a phenomenon of resin properties. The absorption stops once the resin is saturated.

56
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.

57
Q

Dents/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. On sandwich structure, the honeycomb is generally damaged and requires a repair.

58
Q

NDT

A

Non destructive testing

59
Q

Tap testing

A

Detects deboning or trapped water

60
Q

Visual inspection

A

Quick assessment

Surface must be clean

61
Q

Holography inspection

A

Locates small surface defects
Compare a normal to damage specimen
Lots of work to set up

62
Q

Ultra sound inspection

A

Locates internal defects

Quick

63
Q

X Ray inspection

A

Long process

M6 (6 decks)

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