COMPOSITE MATERIALS

Subject: Pre-technical   |   Topic: Materials for Production   |   Target age: 13 (Kenya)

1. What is a composite material?

A composite is made when two or more different materials are joined to make a new material with better properties than the original parts. Each part keeps its own properties but together they are stronger or lighter.

2. Main parts of a composite

• Matrix (binder): The soft material that holds everything together (e.g., plastic, cement, glue).
• Reinforcement: Strong pieces inside (fibres, rods, layers) that give strength (e.g., steel, glass fibres, wood veneers).

3. Common types and Kenyan examples

• Reinforced concrete (concrete + steel): Used in houses, bridges and road culverts across Kenya.
• Glass-fibre reinforced plastic (fiberglass): Used for small boats on Lake Victoria, jiko (stove) parts and basins.
• Plywood (layers of wood + glue): Used for school desks, cupboards and cheap furniture.
• Laminates and laminated glass: Doors, tabletops and some windows.

4. Why use composites? (Advantages)

• Stronger and lighter than single materials — good for boats and roofs.
• Can resist water, chemicals or heat better (depends on materials used).
• Can be shaped into useful forms for products and school projects.

5. Problems with composites (Disadvantages)

• Hard to recycle when they are mixed materials.
• Some types (resins) can be dangerous to work with without safety gear.
• Repair can be difficult; often need specialist skills or tools.

6. Simple ways composites are made

• Lay-up: Layers of fibres laid into a mould and coated with resin (used for small boats and basins).
• Pouring: Concrete mixed and poured around steel bars for reinforced concrete.
• Lamination: Layers of wood glued and pressed to make plywood.

7. Classroom activity (easy and safe)

Goal: Make a simple laminated sheet and test how strong it is.

1. Materials: 4–6 sheets of newspaper, PVA school glue, a flat board, a heavy book or two.
2. Method: Brush glue on each sheet and press the sheets on top of each other to form a stack. Put under a flat board and place heavy books on top. Let dry 24 hours.
3. Test: Try bending the dried laminate. Compare its strength to a single sheet of paper. Discuss why the laminate is stronger.

Safety: Use school glue and do the activity in a clean area. If using resin or chemicals (not needed for this activity), wear gloves and work with adult help.

8. Care and maintenance

• Keep composite surfaces clean and dry to avoid damage (e.g., clean fiberglass boats after saltwater use).
• Repair small cracks early to stop them growing.
• Use recommended paints or coatings for weather protection.

9. Quick glossary

• Matrix: Material that holds reinforcements together (glue, resin, cement).
• Reinforcement: Strong material inside (steel bars, fibres, wood layers).
• Ply: One layer of wood in plywood.
• Fiberglass: Glass fibres used to strengthen plastics.

10. Short quiz (check your answers)

1. What are the two main parts of a composite?
2. Name one composite used on boats in Kenya.
3. Why is reinforced concrete used in building schools?
4. Give one disadvantage of composites.
5. Describe a safe classroom activity to show how composites can be stronger.

Use these notes to help with classwork and projects. Ask your teacher about safe materials for practical work and always work with an adult when using chemicals or tools.