✅3.5 - Composites

Question 1

What is a composite?

Answer 1

A material that is made from two or more materials which have significantly different physical or chemical properties; when combined they create a single material which is often lighter and stronger that the original materials on their own

Question 2

Why are composites used?

Answer 2

Because they can be engineered to meet the exact requirements of a specific application

Question 3

Examples of early composites (2)

Answer 3

• Combining mud (wet soil or clay) with plant material such as straw to make bricks
• Concrete, comprised of small stones and gravel with cement and sand

Question 4

Three main composite groups (modern composites)

Answer 4

• Carbon-fibre Reinforced Polymers (CFRP)
• Glass-fibre Reinforced Polymers (GRP)
• Aramid products (Kevlar®)

Question 5

Glass-fibre Reinforced Polymers (GRP)

Answer 5

A relatively composite material, also known as fibreglass which is made from strands of glass which form a flexible matrix or fabric

Question 6

Benefits of GRP

Answer 6

• Strong compared to its weight
• Corrosion resistant
• Water resistant
• Variation during manufacture in the thickness of layers can produce different weights and strengths
• Suited for batch productions

Question 7

Kevlar®

Answer 7

One of a family of materials developed froma synthetic fibre created by chemist Stephanie Kwolek in 1965; formed by combining paraphenylenediamine and terephtaloyl chloride to result in a super stiff, heat resistant polymer that is nine times stronger than nylon

Question 8

Benefits of Kevlar®

Answer 8

• Lighter
• Stronger
• Flexible
• High performance
• Safer
• Natural toughness allows fabrics and threads to stand up to repeated abuse
• Helps minimise vibration transfer
• Can sustain deformation without breaking

Question 9

Carbon-fibre Reinforced Polymers (CFRP)

Answer 9

One of the most expensive composite materials but boasts the best strength to weight ratio of any construction material; it is made from high tensile strength carbon fibres which are woven together and then encased in a polymer resin

Question 10

Benefits of CFRP

Answer 10

• Resistant to stretching
• Rigid
• Light in weight yet strong
• High tolerance to heat

Question 11

Examples of where GRP is used (5)

Answer 11

Manufacture of:
- Car bodies
- Water tanks
- Swimming pool slides
- Canoes
- Boat hulls

Question 12

Examples of where Kevlar® is used (2)

Answer 12

Manufacture of:
- Garments, mostly known for bullet-proof vests
- Personal Protective Equipment (PPE), used to protect people working in hazardous jobs

Question 13

Examples of where CFRP is used

Answer 13

Manufacture of products in the:
- Marine industry
- Automotive industry (e.g. Formula 1 car bodies)
- Defence industry
- Sports and leisure industries (e.g. sporting prosthetic limbs)