Describe Composites
Composites are a combination of two or more materials that are bonded together to improve their chemical, physical, mechanical or electrical properties.
Define Fibre
Fibres are a class of materials that are continuous filaments or are in discrete elongated pieces, similar to lengths of thread with a length to thickness ratio of at least 80.
Describe the matrix composition of composites
The "Matrix Composition" of composites refers to how composite materials are formed together. A composite is a material that has been combined with two or more other materials to improve the properties of the materials. When one material is embedded into another material, the product is a composite. The separate materials then reinforce each other, resulting in an overall stronger and more useful material.
It is where one material acts as a glue 'matrix' holding the other material in place, such as Glass reinforced fibre (fibreglass).
Explain that new materials can be designed by enhancing the properties of traditional materials to develop new properties in the composite material
It is possible to enhance the properties of a material by adding another material with the properties that are wanted, an example would be improving the toughness of concrete by adding steel rods. concrete is hard (high compressive strength) and weak in tension but steel is tough and has high tension but not too hard, therefore by adding steel to concrete, we get a hard and tough composite material that is ideal for building. Something important to consider when making composites is thermal expansivity as two materials with different rates of expansion would break each other.
Describe a smart material
Smart materials have one or more properties that can be dramatically altered, for example, viscosity, volume, and conductivity. The property that can be altered influences the application of smart material.
Identify a range of smart materials
Smart materials include piezoelectric materials, magneto-rheostatic materials, electro-rheostatic materials, and shape memory alloys. Some everyday items are already incorporating smart materials such as coffee pots, cars, the International Space Station, eye glasses, and the number of applications for them is growing steadily.
Here is an example of a smart material. It is specifically a shape memory alloy, which you can read more about below. If you watch the first minute or so, you'll get the idea of how it works. Watch further for more detail into where it can be used in real life situations, although it is formatted like an advertisement!
Describe a piezoelectric material
When a piezoelectric material is deformed, it gives off a small electrical discharge. When an electric current is passed through it, it increases in size (up to a 4% change in volume). They are widely used as sensors in different environments. Specific details of crystalline structure are not required.
Outline one application of piezoelectric materials
Piezoelectric materials can be used to measure the force of an impact, for example, in the airbag sensor on a car. The material senses the force of an impact on the car and sends and electric charge to activate the airbag.
Describe electro-rheostatic and magneto-rheostatic materials
Electro-rheostatic (ER) and magneto-rheostatic (MR) materials are fluids that can undergo dramatic changes in their viscosity. They can change from a thick fluid to a solid in a fraction of a second when exposed to a magnetic (for MR materials) or electric (for ER materials) field, and the effect is reversed when the field is removed.
Outline one application of electro-rheostatic materials and one application of magneto-rheostatic materials
MR fluids are being developed for use in car shock absorbers, damping washing machine vibration, prosthetic limbs, exercise equipment, and surface polishing of machine parts.
ER fluids have mainly been developed for use in clutches and valves, as well as engine mounts designed to reduce noise and vibration in vehicles.
Describe shape memory alloys (SMAs)
SMAs are metals that exhibit pseudo-elasticity and shape memory effect due to rearrangement of the molecules in the material. Pseudo-elasticity occurs without a change in temperature. The load on the SMA causes molecular rearrangement, which reverses when the load is decreased and the material springs back into its original shape.
Here is an example of a shape memory plastic:
Identify applications of SMAs
Applications for pseudo-elasticity include eye glasses frames, medical tools and antennas for mobile phones. One application of shape memory effect is for robotic limbs (hands, arms, legs). It is difficult to replicate even simple movements of the human body, for example, the gripping force required to handle different objects (eggs, pens, tools). SMAs are strong and compact and can be used to create smooth lifelike movements. Computer control of timing and size of an electric current running through the SMA can control the movement of an artificial joint. Other design challenges for artificial joints include development of computer software to control artificial muscle systems, being able to create large enough movements and replicating the speed and accuracy of human reflexes.
