1. 7.1 Properties of materials
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2. Properties of materials
Different materials have different properties. This means that each material might perform differently when tested or used in the same way. When designing a product, you need to choose materials by their properties. The first step towards doing this is to look at the design needs in your specification.
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3. Properties of materials
Your design needs will tell you what the product you are designing has to do, the type of environment that it will be used in, and how long it is expected to last. For each need, you should identify the properties that the material the product will be made from must have.
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4. Which material properties?
Design question
Property
Does the material have to withstand forces, such as loads being put on it, being pulled or being twisted?
Strength
Does the material need to be resistant to scratches and wear?
Hardness
Does the material need to be resistant to knocks and bumps?
Toughness
Does the material have to withstand wear and tear?
Durability
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5. Which material properties?
Design question
Property
Does the material have to be light, so that it can be moved easily or carried around?
Weight
Does the material need to be a in a certain price range?
Cost
Does the material have to work in an environment that could damage it?
Corrosion resistance
Does the material need to allow electricity to pass through it?
Electrical conductor
Does the material need to stop heat from passing through it?
Thermal insulator
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6. Which material properties?
Example 1: If you were designing a bridge over a river, you might decide that the materials used needed to be strong, tough and resistant to corrosion from water.
Example 2: If you were designing a tyre for a car, you might decide that the important properties were that it should be hard (resistant to wear), tough and low cost.
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7. Which material properties?
Many products need a material to have a combination of different properties. It can be hard to identify a material with exactly the right combination, so designers often compromise. For example, you might choose a less attractive material because it is stronger; or you might change the design so that it uses a less strong material if it is cheaper.
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8. Classifying materials
Materials can be classified into different groups.
The most common way of doing this is based on what they are made from:
Wood
Metal
Polymers (often referred to as plastics)
Ceramics
Composites.
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9. Classifying materials
It is easy to think that within a group, each material has similar properties. For example, we might believe that all metals are strong or that all polymers are flexible. However, while there may be some typical properties within each group, there will be big differences between individual materials.
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10. Classifying materials
When choosing the best material for a design the material groups can provide a starting point, but the designer must think about the properties of individual materials.
All these products have been designed to be resistant to wear
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11. Smart materials
Some new materials have been developed with properties that change in response to their environment. All of these materials fall into one of the five groups. However, they are often classed as a separate type called smart materials.
A colour-changing thermometer
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12. Summary Materials have many different properties.
The designer needs to choose materials which meet the properties needed by the product.
Materials are commonly classified into five groups: wood, metals, polymers, ceramics and composites.
Within each group, there may be big differences in the properties between different materials.
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