Composite Materials: GRP, Carbon Fibre, Concrete & MDF

This lesson covers composite materials — materials made by combining two or more different materials to produce a new material with enhanced properties. Composites are an important topic in AQA GCSE Design and Technology (8552), Section 3.1.3.

---

What Is a Composite Material?

A composite is a material made from two or more constituent materials with significantly different physical or chemical properties. When combined, they produce a material with characteristics different from — and usually superior to — the individual components.

Most composites consist of:

• A matrix (binder) — the material that holds everything together
• A reinforcement (fibre or particle) — the material that provides strength or stiffness

Component	Role	Example
Matrix	Binds the reinforcement, transfers loads, protects fibres	Polyester resin, epoxy resin, cement
Reinforcement	Provides strength, stiffness or other mechanical properties	Glass fibres, carbon fibres, steel bars, wood particles

---

GRP (Glass Reinforced Plastic) — Fibreglass

GRP (commonly called fibreglass) is a composite made from glass fibres embedded in a polyester resin matrix.

Properties of GRP

Property	Detail
Strength-to-weight ratio	Excellent — strong but lightweight
Corrosion resistance	Does not rust or corrode; unaffected by seawater
Mouldability	Can be formed into complex shapes using moulds
Electrical insulation	Does not conduct electricity
Durability	Resistant to weathering and UV degradation

How GRP Is Made (Lay-Up Process)

1. A mould is prepared and coated with a release agent.
2. A layer of gel coat (coloured resin) is applied for a smooth surface finish.
3. Layers of glass fibre mat are laid into the mould.
4. Polyester resin is brushed or rolled onto the glass fibre, saturating it.
5. Steps 3–4 are repeated to build up thickness.
6. The composite is left to cure (harden) at room temperature or in an oven.
7. The finished part is removed from the mould and trimmed.

Applications of GRP

Application	Why GRP Is Used
Boat hulls	Lightweight, corrosion-resistant, can be moulded to complex curves
Car body panels	Lightweight (improves fuel efficiency), resistant to rust
Roofing sheets	Translucent panels allow light through; waterproof
Storage tanks	Chemical resistance; does not corrode
Playground equipment	Tough, weatherproof, low maintenance

AQA Exam Tip: GRP is one of the most commonly examined composites. Remember: matrix = polyester resin, reinforcement = glass fibres. A common exam question asks you to name the two components of GRP and explain the role of each.

---

Carbon Fibre Reinforced Polymer (CFRP)

CFRP is a composite made from carbon fibres embedded in an epoxy resin matrix. It is one of the highest-performance engineering materials available.

Properties of CFRP

Property	Detail
Strength-to-weight ratio	Outstanding — stronger than steel at a fraction of the weight
Stiffness	Very high — resists bending and flexing
Fatigue resistance	Excellent — performs well under repeated loading
Corrosion resistance	Does not rust or degrade in most environments
Thermal stability	Retains properties at elevated temperatures

Applications of CFRP

Application	Why CFRP Is Used
Formula 1 cars	Monocoque chassis provides extreme strength with minimal weight
Aircraft (Boeing 787, Airbus A350)	Reduces aircraft weight by up to 20%, saving fuel
High-end bicycles	Ultra-lightweight frames for racing
Tennis rackets	Stiff, lightweight frames for power and control
Prosthetic limbs	Strong, light, comfortable for the user

Disadvantages of CFRP