Processing of Polymer Matrix Composites (THERMOPLASTIC)

Question 1

What are the conventional processing of reinforced thermoplastic?

Answer 1

Extrusion (for continuous profiles)
Injection moulding for complex parts.

Question 2

What are the aspect of the conventional processing of reinforced thermoplastic?

Answer 2

• Reinforcement makes viscosity higher, so higher pressures needed.
• Greater mould and machine wear.
• Reinforcements need to be compounded in to material first (eg using extruder).
• Cause fibre breakage (limited to 2 mm)
• Low fibre volume fraction (30% max).

Question 3

How does glass mat thermoplastic (GMT) work?

Answer 3

• Similar to sheet moulding compound.
• Short glass fibres or woven roving added to thermoplastic.
• Either at the end of an extruder as a laminating process Or into a thermoplastic slurry.
• Sheets of reinforced thermoplastic produced.

Question 4

What are the benefits of Glass Mat Thermoplastics (GMT)?

Answer 4

• Longer fibres / higher volume fraction than with extrusion or injection moulding.
• Sheets can then be thermoformed.
• Quite widely used in automotive sector.
• More recyclable than SMC / BMC.

Question 5

What is thermoforming?

Answer 5

• Involves heating a flat sheet until it softens.
• Then forcing it into / onto a mould.
• Force applied by pressure, vacuum or matched mould.
• Cooled to stabilise shape.

Question 6

How is pultrusion with thermoplastic, and why is better then pultrusion with thermosets?

Answer 6

• It is possible to modify the pultrusion process to work with thermoplastic.
• Instead of passing fibres through a resin bath, they are drawn through molten thermoplastic.
• Thermoplastic normally fed by an extruder.
• Coating and shaping done together.
• It is a faster process than thermoset pultrusion because the chemical curing of the thermoset is slower than the cooling of a molten thermoplastic.

Question 7

What are twintex?

Answer 7

• Produces co-mingled glass / thermoplastic filament.
• Most common with PP, though PET also available.
• Continuous glass fibres combined with thermoplastic fibres.

Question 8

What are twintex’s properties?

Answer 8

• Glass content 60% or 75% by weight.
• Supplied as roving, woven, fabrics, pellets.
• Or consolidated plates.
• Can then be compression moulded.
• Filament wound.
• Pultruded
• Vacuum formed

Question 9

What is the method of all polymer composite?

Answer 9

• A method of using highly oriented thermoplastic tapes or fibres.
• Woven fabrics laid up (with no separate matrix).
• Heated to melt outer surface of fibres.
• Layer bonded together.

Question 10

How is 3d printing utilised for processing composites?

Answer 10

• 3d printing aka additive manufacturing.
• A process for making a solid object from a three dimensional digital model, typically by laying down many successive thin layers of a matrix.
• Thermoset and thermoplastic matrix materials.
• Print composite materials, such as carbon fibre, Kevlar and fibreglass, which improve the durability and structure of 3d printed products.
• While the process of 3d printing composite materials is not mainstream yet, many manufacturers have started to use it to print everything from car and aircraft parts to the walls of future building.