Manufacturing

Question 1

Describe the process of wet layup.

Answer 1

Apply primer layer (gel coat) to mould.
Place fibre fabric on top.
Spread resin over fabric (by hand or spray gun).

Question 2

Name four advantages of wet layup:

Answer 2

Low cost tooling.
Room temp curing resins.
Can use any combination of fibre and matrix.
Can make large parts with complex geometry.

Question 3

Name four disadvantages of wet layup:

Answer 3

Time consuming and labour intensive.
Safety and hazards less considered (need masks and ventilation).
Resin viscosity must be low enough to work by hand.
Quality is skill dependent.

Question 4

Describe prepreg layup procedure:

Answer 4

Partially cured pre-impregnated fibres are removed from chilled storage.
Uncoiled and layered onto tool surface in preferential orientations.
Debulked.
Cured in autoclave.

Question 5

Name three advantages of prepreg:

Answer 5

Fibres are highly aligned by a machine to maximise mechanical properties.
High fibre volume fraction.
Relatively safer to work with.

Question 6

Name four disadvantages of prepreg:

Answer 6

Must be stored at low temperature to preserve (slow curing).
Debulking takes a long time.
Relatively more expensive for material and curing equipment.

Question 7

Describe compression moulding:

Answer 7

A matched male and female tool set is used, closed by a hydraulic press.
Heat and pressure applied to cure.

Question 8

Name the two compression moulding variations:

Answer 8

BMC - Bulk moulding compound
SMC - Sheet moulding compound

Question 9

Name three advantages of compression moulding:

Answer 9

Automated - high production volume.
Minimal material waste.
Good part uniformity.

Question 10

Name three disadvantages of compression moulding:

Answer 10

Expensive upfront cost for press and tools.
Requires a large press.

Question 11

Describe the filament winding process:

Answer 11

A continuous tow is pulled from a reel and passed through a resin impregnation bath.
Tow then wound over a rotating mandrel.

Question 12

What are the two filament winding variations?

Answer 12

Polar (no crossover)
Helical (perpendicular crossover)

Question 13

Name an advantage and disadvantage of filament winding.

Answer 13

Easily automated for high volume production, therefore low cost.
Can only produce solids of revolution (constant cross sections)

Question 14

Describe the pultrusion process:

Answer 14

Fibres pulled and rearranged to produce composite structures of constant cross section, e.g. I-beam or angle.

Question 15

Name an advantage and disadvantage of pultrusion:

Answer 15

Low operating cost.
Large upfront cost for dies.

Question 16

What are the two categories of liquid composite moulding?

Answer 16

Matched mould.
Single sided mould.

Question 17

What does RIFT stand for?

Answer 17

Resin infusion under flexible tooling.

Question 18

Describe the RIFT procedure:

Answer 18

Dry fibres laid up in desired orientation on flow media.
Resin drawn through from reservoir using a vacuum.

Question 19

Name three advantages of RIFT:

Answer 19

1) Relatively low tooling cost due to one half of the tool being a vacuum bag, and less strength being required in the main tool.
2) Large components can be fabricated.
3) Standard wet lay-up tools may be able to be modified for this process.

Question 20

Name three disadvantages of RIFT:

Answer 20

1) Lots of waste with single use consumables.
2) Resins must be very low viscosity, can compromise mechanical properties.
3) Single sided tool means only one side has good surface finish.

Question 21

What does RTM stand for?

Answer 21

Resin Transfer Moulding

Question 22

Describe the RTM procedure:

Answer 22

Resin injected into a mould.
Fills core and cures.

Question 23

Name three advantages to RTM:

Answer 23

Little waste.
God surface finish on both sides.
Allows for internal cores and in-situ metal structures.

Question 24

Name one disadvantage of RTM:

Answer 24

Long production cycle.

Question 25

What consumables are used for debulking?

Answer 25

Vacuum bag.
Breather.
Release film.

Question 26

What is release film usually made from?

Answer 26

PTFE.

Question 27

What are the conditions in an autoclave for thermosets?

Answer 27

Temp: 100 to 200 C
Pressure: 500 to 700 kPa

Question 28

What are the conditions in an autoclave for thermoplastics?

Answer 28

Temp: 300 to 400 C
Pressure: 1000 kPa

Question 29

Name two advantages to use of an autoclave:

Answer 29

Produces high quality parts.
Good for large parts.

Question 30

Name four disadvantages to use of an autoclave:

Answer 30

Not good for high volume production.
Debulking often time consuming.
Energy inefficient as need heat and pressure.
Limited to prepregs.