6.3 Composite And Non Metallic

Question 1

What is the term composite used to describe

Answer 1

Two or more materials that are formed to make a stronger structure than either material by itself

Question 2

What 2 elements does a basic composite consist of

Answer 2

• Matrix (Adhesives or resin)

- A reinforcing material (Fabric)

Question 3

What type of form would a matrix normally come in

Answer 3

A liquid form

Question 4

What are the 4 main advantages of composites

Answer 4

• High strength to weight ratio
• Reduction in parts and fasteners
• Reduction of wear
• Corrosion resistance

Question 5

What are the 2 main disadvantages of composites

Answer 5

• Expensive to repair

- Requires specialist equipment and people to carry out a repair

Question 6

What are the advantages of nomex

Answer 6

High temperature resistance

Question 7

What is nomex used for

Answer 7

Flame proof clothing

Question 8

What are the 2 main types of fibreglass used

Answer 8

• S glass

- E glass

Question 9

What properties do S glass and E glass have

Answer 9

S glass - Very High tensile strength

E glass - Highly resistant to electricity

Question 10

What are the characteristics of aramid also known as aromatic polyamide

Answer 10

• Yellow in colour
• Light weight
• Excellent tensile strength

Question 11

If aramid structures get damaged what can be used to repair them

Answer 11

Generally fibreglass

Question 12

What is Kevlar mainly used for

Answer 12

Bullet proof vests and radial tyres

Question 13

What are the main disadvantages of Kevlar

Answer 13

• The fibres absorb moisture

- not great in compression

Question 14

What happens when Kevlar fibres are exposed to sunlight

Answer 14

They will turn from a gold/yellow to brown. Kevlar is very sensitive to sunlight

Question 15

What are the biggest advantages of carbon fibre

Answer 15

• High strength
• Low density
• Low fracture resistance
• High temp resistance

Question 16

What are the biggest disadvantages of carbon fibre

Answer 16

• Wears out steel cutting blades

- Requires skilled tooling and personnel to make

Question 17

What is used between graphite and aluminium to help prevent corrosion

Answer 17

A layer of fibreglass

Question 18

Resins are a type of plastic broken down in to which two categories

Answer 18

• Thermoplastic

- Thermoset

Question 19

How do thermoplastics work

Answer 19

They can be reshaped with the addition of heat

Question 20

How do thermosets work

Answer 20

Once they have been heated and set the shape is permanent. Composites such as carbon fibre are made with thermoset resins

Question 21

When would epoxy resins be used

Answer 21

When bonding metal and composite or two dissimilar materials

Question 22

What is the purpose of a honeycomb structure

Answer 22

Great strength to weight ratio

Question 23

What can honeycomb constructions be made from

Answer 23

Aluminium, Kevlar, carbon, fibreglass, nomex and steel

Question 24

What are the 4 main ways manufacturers use for dissipating electrical charge on composite components

Answer 24

• Flame spray
• Bonding jumpers
• Aluminium wires woven in to the top layer
• Thin Aluminium foils bonded on the top layer

Question 25

What type of information would be found on the Material Safety Data Sheet (MSDS)

Answer 25

- Health precautions - Flammability of the material - Ventilation requirements - Information for health professionals in event of emergency

Question 26

How are plastics made

Answer 26

- Polymarisation - Polycondensation - Polyaddition

Question 27

How does polymerisation work

Answer 27

A chemical reaction carried out in the presence of a catalyst which makes small molecules into a long chain

Question 28

What important polymers are made by polycondensation

Answer 28

- Bakelite - Nylon - Polyester

Question 29

What important polymers are made by Polyaddition

Answer 29

- Polyurethane | - Epoxies

Question 30

What is the advantage of adhesives

Answer 30

Cheap, strong, efficient, corrosion resistant, eliminates the requirement of fasteners

Question 31

What is aerosil

Answer 31

Used as a thrixatropic agent in resins to thicken them up

Question 32

Must what happen to solvent adhesives for them to set

Answer 32

The solvent must evaporate

Question 33

What are dispersion adhesives used for

Answer 33

Wood glue or paste

Question 34

What are film adhesives

Answer 34

Come on a roll and are similar to pre preg

Question 35

What are thixotropic agents

Answer 35

A thickening agent

Question 36

What are the 2 most common thixotropic agents used

Answer 36

- Aerosil | - Micro balloons

Question 37

When mixing resins how are the ingredients measured

Answer 37

By weight, mixing should take 3-5 mins

Question 38

Where would phenolic resins be used

Answer 38

In cabins due to their fire resistance

Question 39

What should not be mixed directly together to prevent a fire

Answer 39

Catalyst and accelerator. This will have an exothermic reaction

Question 40

When investigating damage on a composite panel what documentation should be used

Answer 40

The SRM

Question 41

What are the 3 categories of composite damage when it is initially assessed

Answer 41

- Allowable - Repairable - Not repairable

Question 42

After the composite panel is initially assessed what would the 2 sub categories be in the SRM when assessing composite damage

Answer 42

- Skin not perforated | - Skin perforated

Question 43

What is the difference between a scratch and a gouge

Answer 43

Gouges are deeper and wider than scratches and gouges affect structural strength and scratches don’t

Question 44

What is the principle method for damage detection on a composite panel

Answer 44

GVI

Question 45

What is abrasion

Answer 45

Scuffs, rubbing or scraping

Question 46

Is carbon fibre electrically conductive

Answer 46

Yes

Question 47

Are glass fibres and aramid fibres conductive

Answer 47

No

Question 48

What are the advantages and disadvantages of holography

Answer 48

Advantage - Speed of inspection Disadvantage - Long set up time

Question 49

When are ultrasonics used in NDT

Answer 49

Quick and inexpensive assessment of composite parts

Question 50

What is the purpose of radiography

Answer 50

Quick and inexpensive examination of composite structures

Question 51

What are the 3 recommended types of repairs for composite structures

Answer 51

- Temporary repairs - Permanent cosmetic repairs - Permanent structural repairs

Question 52

When prepping composite panels for repair how should the surface protection be removed

Answer 52

By mechanical means only, use of chemicals may damage the composite

Question 53

When removing damage from composites how should it be done

Answer 53

By one layer at a time (scarfing)

Question 54

What is wet lay up

Answer 54

Applying several layers of material impregnated with resin applied straight to the surface

Question 55

What is shelf life

Answer 55

How long the product is good for in an unopened container

Question 56

What material is used for vacuum bagging due to its high tensile strength

Answer 56

Nylon

Question 57

What is the purpose of peel ply

Answer 57

Improves surface finish on a composite repair

Question 58

What is the purpose of a caul plate when carrying out a composite repair

Answer 58

- Evenly distributes temperature - Even out pressure over the whole repair - To improve the flatness of the surface

Question 59

What is a heater blanket

Answer 59

An electrical pad which regulates the temperature of a composite repair