Engineering Materials

Materials and Materials Research

Making any project in Engineering involves using some type of material.

The picture, drawn by Mr Mckenna who probably needs to get out more, clearly shows the wide range of facts and issues that engineers consider in the very early stages of creating any product.

As an engineering student it is essential that you carry out research into materials, and record what you have found out in your own words.

The Environment

Materials are carefully selected to ensure that they do not harm the environment in which they are used.

Protecting Materials

Materials can be protected from rusting, oxidation or rot with surface coatings or the addition of other materials.  

Metals

There are three types of metal:- Ferrous Metal, Non Ferrous Metal and Alloys

Plastics

There are two types of plastic:- Thermosetting Plastic and Thermoplastic

Woods

There are two types of wood:- Natural woods and manmade woods

Smart Materials

These are modern materials that have amazing properties. They can be metal, wood or plastic, or a combination. They can re-shape and be reformed. They can be engineered to react to temperature changes and changes in electrical current.

Material Properties

When selecting the correct material for a project it is very important to have an understanding of material properties.

A material “Property” determines how a material will behave when being used. A material that is being used will be subjected to some type of force.

Forces can make the material bend, twist, expand, contract, deform and ultimately break.

The different Properties are Strength, Elasticity, Plasticity, Ductility, Tensile Strength, Malleability, Toughness, Hardness and Conductivity.

Metals

There are three types of metal; Ferrous, Non-Ferrous and Alloy.

Ferrous metals contain Iron and are magnetic. Altering the carbon content of ferrous metals will change the working properties of the material.

Non-Ferrous metals do not contain and are not magnetic. They generally softer and more ductile than ferrous metals and can have lower melting points.

Alloys are made by combining two or more different metals together. The resulting material will have improved properties that the engineer is seeking.

Plastics; Thermosetting and Thermoset.

There are two types of plastic; Thermosetting and Thermoset plastic.

To make a Plastic, or a polymer the materials engineer joins lots and lots of monomers together.

Plastics are versatile and flexible materials. All plastics are based on polymers and they are created by bonding molecules together.

The terms monomer and polymer are very important in the plastics industry.

A MONOMER is a small molecule that combines chemically to other monomers to form a polymer

Remember, all plastics are polymers.

Example - derived from oil - a hydrocarbon ethylene molecule can be seen in the diagram

Many modern plastics are manufactured from oil.

EXAMPLE THERMOSETTING PLASTICS

The Thermoset Plastic

Once 'set' these plastics cannot be reheated to soften, shape and mould. The molecules of these plastics are cross linked in three dimensions and this is why they cannot be reshaped or recycled. The bond between the molecules is very strong.

Many adhesives (glues) are thermosetting plastics. A good example is ‘Araldite’ which is an epoxy resin that hardens when a second chemical is added (a catalyst). It will bond most materials including woods and metals as well as some plastics.

 

EXAMPLE THERMOPLASTICS

The Thermoplastic

These plastics can be re-heated and therefore shaped in various ways. They become mouldable after reheating as they do not undergo significant chemical change. Reheating and shaping can be repeated. The bond between the molecules is weak and become weaker when reheated, allowing reshaping. Thermoplastics tend to be composed of 'long chain monomers'. These types of plastics can be recycled.

These plastics possess a common property, they soften when heated and are often used in schools to vacuum form shapes. Usually, when heated and formed into a shape - if reheated they return to their original shape. 

Woods and Man Made Woods

 

Smart Materials