Carbon Fibre Composites

Question 1

Definitin

Answer 1

materials made from two or more constituents with significantly different physical or chemical properties that, when combined, produce a material with characteristics different from the individual components. The individual components remain separate and distinct within the finished structure

Question 2

Composite Raw Materials

Answer 2

Reinforcements: fabrics and individual fibres
Resin matrices: thermosets and thermoplastics
Core materials: honeycomb, foam and natural
Bulk out the structure whilst allowing it to remain lightweight

Question 3

Carbon Fibre Manufacture

Answer 3

Oxidise & Carbonise
High energy is required to run furnaces
Slow process – heat and tension
Surface treatment
‘Finish oils’ – top secret!
Sizing
Protect and compatibilise fiber
Process conditions define properties:
High Strength
High Modulus
Intermediate Modulus
Winds in a helical pattern to ensure no tangling and an even tension application

Question 4

Making Prepreg: solvated Prepreg

Answer 4

Certainly! Here’s a shorter overview of making solvated prepreg:

1. Resin Selection: Choose a thermosetting resin (e.g., epoxy) and a suitable solvent (e.g., acetone).
2. Resin Mixing: Mix the resin with the solvent to create a solution.
3. Fiber Impregnation: Pass reinforcing fibers (e.g., carbon fibers) through the resin solution to impregnate them.
4. Solvent Evaporation: Remove the solvent by controlled drying to leave behind resin-impregnated fibers.
5. B-Stage Curing: Partially cure the prepreg to a tacky, semi-solid state (B-stage) for handling and storage.
6. Cutting and Packaging: Cut the prepreg into desired shapes and package for further processing.

The resulting solvated prepreg is ready for use in manufacturing composite parts with high strength and durability.

High-volume, low-cost process
Residual solvent which is hazardous
Environmental impact

Question 5

Hot Melt Prepreg

Answer 5

Start with resin filming: make resin in the exact thickness and distribution required
Impregnation: two of these rolls are used, one above and one below.

Question 6

Making Parts with Composites: Infusion/Liquid Composite Moulding

Answer 6

Liquid resin added to dry fibres in a simple tool.

cheap raw material
low pressure, simple tooling
room temp cure

higher labour cost
slow cure times
tough to control exotherm/temp throuhg the thickness
Needs low viscosity resins

Question 7

Compression Moulding

Answer 7

Matched tooling used to apply high pressure and temperature to a preformed stack of material – SMC or prepreg

potentially v fast cure time
parts have 2 good surfaces
good dimensional control

High cost, complex toolinh
material flow needs to be tailored
Tricky to achieve tight corners
not suitable for very lage parts

Question 8

Prepreg Layup

Answer 8

Resin pre-impregnated reinforcement, typically thermoset (epoxy) UD tape for cure in autoclave, automatically laid-up (ATL, AFP) for aerospace applications
☺ Resin/catalyst levels accurately set from the material supplier → high and predictable properties
☺ Optimised fibre use as UD fibre is aligned to structural loads
☺ Can use high viscosity resins for high toughness and damage tolerance
☺ Allows complex lay-ups in automated processes
😒 Higher material cost from multi-step process and cold supply chain
😒 Needs expensive tooling capable of withstanding high temperature and pressures
😒 Debulking need on thicker laminates

Question 9

Core/Honeycomb Manufacture

Answer 9

Gives stiffness and rigidity whilst still being very light

Good compression strength

Manufacture by offsetting the adhesive so when it is pulled apart, it will have the honeycomb structure