8.4Composite Materials and Their Importance
A composite material is created by combining two or more non-homogeneous substances: a matrix substance and a strengthening substance. The matrix surrounds and binds the strengthening substance together. The resulting composite material exhibits superior physical and chemical properties compared to its individual original components.
Learning Objectives
- State the meaning and properties of composite materials.
- Describe with examples the uses of composite materials.
- Compare and contrast the properties of a composite material with its constituent materials.
Comparison of Composite Materials and Their Constituent Substances
Identify the matrix and strengthening components of each composite material and observe how their combined properties outperform the individual components.
Reinforced Concrete
Matrix: Concrete
Strengthening: Steel bars / wire mesh
Combined property: High compression strength, high stretching strength, resistant to corrosion.
Fibre Glass
Matrix: Plastic
Strengthening: Glass fibres
Property comparison: Plastic and glass fibres have low and high stretching strength respectively, and both have low heat and electrical conductivity. Fibre glass combines high stretching strength, insulation, corrosion resistance and durability.
Optical Fibre
Matrix: Cladding (glass/plastic) + protective jacket (plastic)
Strengthening: Silica glass fibres (core)
Property comparison: Plastic has high compression strength and is flexible; glass fibre has low compression strength, is flexible, hard and brittle. Optical fibre has high compression strength and flexibility and transmits data as light.
Photochromic Glass
Matrix: Glass
Strengthening: Silver chloride and copper(I) chloride
Property comparison: Glass does not absorb UV radiation and is not light-sensitive; silver chloride absorbs UV radiation and is sensitive to light intensity. Photochromic glass absorbs UV radiation depending on light intensity.
Superconductor (YBCO)
Original components: Yttrium(III) carbonate, barium carbonate, copper(II) carbonate and oxygen. The textbook does not designate these components as a matrix or strengthening substance.
Property comparison: The original components have high electrical resistance at room temperature; YBCO has no electrical resistance at very low temperatures.
Brief Explanation
Understand the key ideas behind composite materials.
Natural Composite Materials
Wood: Formed from lignin and cellulose fibres. It is strong and sturdy.
Teeth: Made up of hydroxyapatite and collagen.
Reinforced Concrete Example
Concrete is strong under compression but weak under tension, whereas steel is strong under tension but prone to rust. When combined into reinforced concrete, the resulting composite is resistant to compression, strong against stretching, and protected from corrosion.
| Composite Material | Matrix Substance | Strengthening Substance | Uses |
|---|---|---|---|
| Reinforced Concrete | Concrete | Steel bars or wire mesh | Construction of bridges, dams, and buildings |
| Fibre Glass | Plastic | Glass fibres | Helmets, car bumpers, and printed circuit boards |
| Optical Fibre | Cladding (glass/plastic) + protective jacket (plastic) | Silica glass fibres (core) | Replaces copper wires in video cameras and connects computers in Local Area Networks (LAN) |
| Photochromic Glass | Glass | Silver chloride and copper(I) chloride | Car windows, building windows, and camera lenses |
| Superconductor (YBCO) | Original components: Yttrium(III) carbonate, barium carbonate, copper(II) carbonate and oxygen; no matrix/strengthening roles assigned | Particle accelerators, NMR machines, and MRI machines | |
Try to Answer First
Answer mentally, then check the explanation.
Name the matrix substance and strengthening substance found in natural wood.
Why does photochromic glass darken when exposed to sunlight?
What is the key electrical property difference between YBCO superconductor and its original carbonate components?
Common Mistakes
Avoid these errors when studying composite materials.
Concept Misunderstandings
Compare each misconception with the correct fact.
A composite material is a chemical compound or a homogeneous mixture like an alloy.
A composite material consists of two or more distinct, non-homogeneous phases (matrix and strengthening substances) that remain physically separate while acting together.
Optical fibres transmit data using electric currents.
Optical fibres transmit information and data in the form of light via total internal reflection, not electric current.
Summary
Key facts to remember.
- A composite material combines a matrix substance (binder) and a strengthening substance (reinforcement) to produce superior properties.
- Natural examples: Wood (lignin + cellulose fibres) and Teeth (hydroxyapatite + collagen).
- Reinforced concrete: Concrete + steel bars/wire mesh (high compression and stretching strength).
- Fibre glass: Plastic + glass fibres (high stretching strength, durable, insulator).
- Optical fibre: Core of silica glass fibres + cladding of glass/plastic + protective jacket of plastic (transmits data as light, high compression strength, flexible).
- Photochromic glass: Glass + silver chloride and copper(I) chloride (darkens in sunlight, UV protection).
- Superconductor (YBCO): Metal carbonates + oxygen (zero electrical resistance at very low temperatures).
Short Activity
Complete all parts before checking your score.
A. Objective Quiz
Which of the following correctly pairs the composite material with its strengthening substance?
What is the function of copper(I) chloride in photochromic glass?
B. Fill in the Blanks
Light moves through the core section of an optical fibre in a series of total internal ________.
A superconductor composite such as YBCO ceramic conducts electrical current with zero electrical resistance at very ________ temperature.
C. Match the Composite Material with Its Use
Drag each composite material on desktop. On mobile, tap a material and then tap the matching box.
Composite Material
Reinforced concrete Fibre glass Optical fibre Superconductor (YBCO)Application / Use
Keywords
Tap or hover over a term to read its meaning.
