6.3 - Composite/Non Metallic

Question 1

What are the two basic elements of a composite and what do they do?

Answer 1

Matrix:

• bonding substance
• transfers stress to the fibre

Reinforcing material(fabric)

Question 2

What are the advantages and disadvantages of composites?

Answer 2

+high strength to weight ratio
+reduction in fasteners
+corrosion resistance

• expensive
• not easy to repair

Question 3

What is the main purpose of the reinforcing material?

Answer 3

Gives the major strength to the composite material

Question 4

What is Nomex used for?

Answer 4

Flame-proof clothing due to its high heat resistance

Question 5

What are the two main Fibreglass types and what are their perks?

Answer 5

E-glass: electricity resistant

S-glass: high tensile strength

Question 6

What are the main characteristics of fibreglass?

Answer 6

• low density
• high strength
• NOT water/humidity resistant

Question 7

What are the main characteristics and uses of Aramid?

Answer 7

• yellow
• light weight
• high tensile strength
• non-flammable
• used in high vibration/stress areas
  e. g. props

Question 8

What are the main uses of Kevlar?

Answer 8

Bulletproof vests

Belts for radial tyres

Cables

Reinforced composites for aircraft

Question 9

What are the main disadvantages of Kevlar?

Answer 9

-fibres absorb moisture
-not compression
resistant
-difficult to cut
-UV sensitive(turns brown)

Question 10

What is main property of Carbon Fibre?

Answer 10

Electrical conductivity

Question 11

What is the orientation of the Warp?

Answer 11

Threads run along the length

Question 12

What is the orientation of the Weft?

Answer 12

Perpendicular to the Warp

Question 13

What is the selvage edge?

Answer 13

Tightly woven edge, runs parallel to the Warp

Question 14

What is the bias?

Answer 14

Runs 45deg to the Warp, allows for the creation of complex contours.

Question 15

What are Unidirectional Fibres?

Answer 15

The major fibres run in the direction of the Warp

Question 16

What are Bi-Directional Fibres?

Answer 16

The fabric runs in two or more directions

Question 17

What is the newer type of matrix?

Answer 17

Epoxy resins

Question 18

What are the two categories of Resins?

Answer 18

Thermoplastics

Thermosets

Question 19

What is a thermoplastic?

Answer 19

Once heated, the final shape is not permanent

Question 20

What is a thermoset?

Answer 20

Once heated the final shape is permanent

Question 21

What is an Epoxy resin?

Answer 21

A type of thermoset plastic resin, used to bond dissimilar materials

Question 22

What is Prepreg?

Answer 22

• Pre-impregnated fabrics
• already have the resin in them
• stored in a freezer

Question 23

What is a ‘sandwich’ construction?

Answer 23

The core is bonded between two thin sheets, makes a light weight, rigid structure

Question 24

What are the two honeycomb fabrication processes?

Answer 24

• corrugated

- expansion

Question 25

What is Polymerisation?

Answer 25

Creating a long chain of Molecules from small Monomers, doesn’t create any by-products.

Question 26

What is Polycondensation?

Answer 26

Removes by-products such as water/acids

Question 27

What is Polyaddition?

Answer 27

Reaction of different molecules when reactive groups are brought together.

Question 28

What is a Thixotropic agent?

Answer 28

A thickening agent

Question 29

Name two examples of Thixotropic agents?

Answer 29

Micro-balloons Aerosil

Question 30

What considerations must taken when mixing resins?

Answer 30

Never mix in a wax container Always weigh at an ambient temperature Mix between 3 and 5 minutes Do not mix too quickly, bubbles may form

Question 31

What is BVID?

Answer 31

Barely Visible Impact Damage

Question 32

What is Delamination?

Answer 32

The separation of composite surfaces, damage may not be visible on the surface.

Question 33

Name examples of NDT’s

Answer 33

``` Tap testing Visual Bond tester Ultrasonic Radiography (X-ray) ```

Question 34

What must be remembered when removing surface protection?

Answer 34

Always use mechanical methods, chemical methods can deteriorate the resin.

Question 35

What is Wet Lay-Up?

Answer 35

The application of several layers of resin impregnated fabric over a damaged area.