Composites and Smart Materials Flashcards
What are the three types of composites?
Particle, Laminate, Textile
Give an example of a particle composite
Concrete (sand, water, cement, aggregate)
MDF
Chipboard
Give an example of a laminate composite
Plywood
CFRP (carbon fibre reinforced plastic)
GRP (fibre glass and polyester resin)
Kevlar (aramid)
Give an example of a textile composite
Gore tex
- polyester/nylon
- PTFE/Teflon
Advantages of GRP
- Cheaper than the other composites
- Lightweight, corrosion resistant, easily processed and good mechanical properties.
- Generally easy to manufacture and build items from.
- Often used in combination with another material to provide additional support
What is GRP made of
chopped up glass strands from mat form combined with polyester resin
Disadvantages of GRP
Brittle - impact will cause cracking and it is difficult to repair - it usually means the part will have to be replaced
What is Kevlar?
Strong artificial fibre (aramid carbon fibre composite) which can be woven into materials that is used for light and flexible body armour, but also used in sport equipment
What is carbon fibre (CFRP)?
Can be in a strand form, a fibre form or woven into a sheet form. Often combined with phenolic, polyurethane or epoxy resins as the matrix
Advantages of Kevlar
- Strong tensile strength but very flexible as the molecules can pack closely together.
- Tough - very resistant to impact and abrasion damage, hence its use in bullet and stab proof vests - but also used in sports gear as it is good at resisting high velocity objects like balls.
- Can be made waterproof when combined with other matrix materials like epoxy.
- Can also be combined with rubber to increase the flexibility of sports equipment.
Disadvantages of Kevlar
Poor compressive strength
Frays easily
Advantages of CFRP
- High temperature resistance
- Corrosion resistance
- Lightweight
- High mechanical strength
- High strength to weight ratio
- Due to strength can be made in very thin sections so it is lightweight. Can be made in thinner sections than other composites.
Disadvantages of CFRP
- More expensive than most other composites
- Often used to create stiffness in equipment. Greater stiffness resists bending forces and transfers more power to an object (useful in sports equipment).
- Not especially tough does not resist impact forces well and tends to break. Often combined with Kevlar to resist this. This composite is very strong but flexible and expensive)-
What is gore tex?
A synthetic waterproof fabric permeable to air and water vapour
How does gore tex work?
There is a microporous membrane which allows water vapour to pass through but not water droplets so it it breathable and waterproof
Advantages of gore tex
waterproof
breathable
lightweight
durable
Disadvantages of gore tex
Can be expensive
Hard to care for (should be cleaned)
Not absorbent
What is nomex?
A flame-resistant aramid material, e.g. used for firefighter’s suits
Advantages of Nomex
Heat Proof
Durable
Extremely strong in tension and tough
Disadvantages of nomex
Not absorbent
Weak in compression
Can be expensive
Give 3 examples of smart/modern materials
- thermochromic and photochromic inks
- shape memory polymers
- phosphorescent materials
Describe a use for a thermochromic ink
Used on kettles - shows when water is hot so you don’t need to reboil your kettle
Used on baby thermometers - place strip of paper with these inks on forehead and it will change colour according to temperature, means you don’t need to stick a thermometer in young babies mouth
Describe a use for photochromic inks
Glasses for indoor and outdoor use (Reactolite Lenses) - change with light intensity to go darker when there is high UV to protect retinas from direct sunlight, acts as sunglasses with prescriptions
Describe an example of a shape memory alloy
Medical equipment - tube is cooled and squashed into a smaller tube. it is inserted into an artery and will expand due to body heat keeping the channel open for blood flow
Car bumpers - if in a crash, metal can be heated and it returns the shape. It is still strong to act as a bumper when at normal temperature. Means you don’t need to replace bumpers as much.
What is a shape memory alloy
a metal that can be bent out of its original shape and then returned to its original shape when heated.
