Smart materials and composites

Define what is meant by the term ‘Smart material’? In your answer name a specific smart material and describe a useful physical or mechanical property it has. (2 marks)
- A smart material is a material that changes its form or characteristics when either heat or electricity is applied. One example of this is Nitinol, which is a smart memory alloy (comprised of nickel and titanium), which can be dis-formed then when heated returns back to it's original shape. 

Name a specific smart material and an application for that smart material. (1 mark)
- Thermochromic pigments on the surface of coffee mugs to tell you when the mug is warm.

Define what is meant by the term ‘composite material’ and using examples, describe the general advantages of composites over traditional materials. (2 marks)
- A composite material is something made from several constitutional materials to create a material that has greater propertied than any of the original materials. 


Explain how the structure of plywood gives the material strength. (2 marks)

- Plywood is a laminated material where the grain in the layers are facing opposing directions. This gives the wood strength in all directions. The adhesive glue also aids in the structural integrity of the timber. 

Smart Materials

Steam Bending

Steam Bending:

Most woods can be steam bent. Steam bending is a rather simple process that is exactly what it sounds like, bending wood with steam. Some of the best woods to bend are blackberry, white oak, red oak, magnolia, walnut, pecan, hickory, beech, elm, and birch. Soft woods do not tend to bend as well.

It works by re-adding moisture to the fibres in the wood, this allows them to bend and flex, and therefore they can be moulded. Moisture is added by putting the wood in a rack in a cylinder filled with steam from a pump. There is a general rule of thumb with steam bending, and that is for every inch of wood equals one hour in the steam being cured. So if a piece of wood is five inches thick then it requires five hours in the steam before attempting to bend. After the wood has been cured for the adequate amount of time the wood is removed from the steamer and is clamped around a mould. The moisture is then sucked back out of the wood; this is done through kiln drying. The drying “locks” the fibres in their position bent around the mould. This means the wood retains its bent shape.

The dangers of steam bending are that if the wood is bent before properly cured then it could be at risk of breaking. It also needs to be bent with the grain; if bent against the grain or the wood contains knots then it could also break whilst bending.

The process is used on a small scale making jewellery and one off furniture. But traditionally it was used on a larger scale to form the primary structure for hulls of boats.