Week 9: Composites

Question 1

What is a composite made up of?

Answer 1

Matrix and a filler

Question 2

Matrix

Answer 2

Holds the filler together like a glue
(chocolate in the kit-kat)

Question 3

Filler

Answer 3

Part of the composite to increase elastic modulus, TS and hardness (biscuit in kit-kat)

Question 4

PMC

Answer 4

Polymer matrix composite

Question 5

CMC

Answer 5

Ceramic matrix composite

Question 6

MMC

Answer 6

Metal matrix composite

Question 7

What do the properties of composites depend on?

Answer 7

Volume fraction, particle shape, particle size, size distribution and orientation

Question 8

Are the properties the same in longitudinal and transverse directions?

Answer 8

No, they’re different

Question 9

Longitudinal deformation

Answer 9

Fibers aligned in the longitudinal direction, so stronger there compared to transverse

Question 10

Ultimate TS

Answer 10

TS before failure

Question 11

What does elongation at break measure?

Answer 11

The ductility of a material

Question 12

What does increasing the fiber volume lead to?

Answer 12

+ Impact strength
+ Flexural strength
+ Storage modulus

Question 13

PFRP

Answer 13

Natural composites

Question 14

GFRP

Answer 14

Glass-fiber reinforced composites

Question 15

CFRP

Answer 15

Carbon-fiber reinforced composites

Question 16

SFRP

Answer 16

Silk-fiber reinforced composites

Question 17

Why is the orientation of fibers important?

Answer 17

It can change the strength of a composite

Question 18

Critical Fiber Length

Answer 18

Length that determines effective stiffness and strength of a composite

Question 19

What are the 2 types of GFRP?

Answer 19

E: electrical - used because of its electrical resistance (ladder)

S: high strength - used in military and aerospace

Question 20

What bonds do aramid fibers have?

Answer 20

Hydrogen bonds

Question 21

What are the 4 main manufacturing processes?

Answer 21

1. Pultrusion
2. Filament winding
3. Closed mould
   4.Open mould

Question 22

Pultrusion

Answer 22

Where continuous fibers are pulled through resin impregnation tank, then pulled to shape

Question 23

Filament Winding

Answer 23

Where continuous fibers are fed though a resin bath and then wound and heated

Question 24

What are the 3 closed mould processes?

Answer 24

1. Injection
2. Transfer
3. Compression

Question 25

Injection moulding

Answer 25

Pellets put through hopper and heated then injected into a mould

Question 26

Transfer moulding

Answer 26

Moved through narrow channels into desired shape

Question 27

Transfer moulding

Answer 27

Moved through narrow channels into desired shape

Question 28

Compression moudling

Answer 28

Resign and filler squashed into desired mould

Question 29

Where are closed mould processes used?

Answer 29

Mass production of identical parts and for smooth surfaces

Question 30

What are some open mould processes

Answer 30

• Hand lay up
• Spray up
• Tape lay up
• Vacuum infusion

Question 31

What are the 5 parameters for successful manufacturing?

Answer 31

1. Choice of matrix (thermoset vs thermoplastic)
2. Low moisture
3. Thermal transition temperatures
4. Resin flow / rheology (viscosity of polymer)
5. Heat of reaction and exotherm

Question 32

What are 3 structural composites?

Answer 32

1. Laminar composites
2. Sandwich panels
3. Nano-composites

Question 33

Laminar composites

Answer 33

Composites arranged in different directions

Question 34

Why are sandwich panels used?

Answer 34

High strength and low ductility

Question 35

What’s a material used to make nano-composites?

Answer 35

Graphene