Uniaxial used for headphones or contact sensors
Uniaxial and biaxial orientation processes are commonly usedto enhance the mechanical properties of thermoplastic materials so that theymay be used in more demanding structural applications. In the past few decades,much research in this area has been devoted to the development of uniaxialorientation, a technique whereby the polymer chains are aligned in onedirection only. This results in significantly improved strength and stiffnessin the direction of orientation, but tensile properties perpendicular to theorientation direction are normally not increasedCB1 .iii) Biaxial film orientation greatly improvesfilm’s tensile strength, flexibility, and toughness. Without orientation, PS istoo brittle to be used as film, and PP loses flexibility in the cold. Orientationalso imparts heat-shrink ability to PS, PVC, and PVDCCB2 .
iv) Typical bodies of modelling stiffness, depending on the type, willhave a water content of between 19.5 and 22.5%. The difference between soft andstiff clay is usually less than 1%. However, water content is not an accuratemeasure of stiffness. Soluble present in the clay, or variations in theelectrolyte in the water supply can cause floccing or defloccing of the puggedclay, so that from one run to the next, identical stiffness’s can have quitedifferent water content figures.
For this reason it is wise to only use thewater content figure as a guide within each clay run.v) Concrete has a low tensilestrength when stretched for this reason when concrete is used for example onmotor ways or football grounds where strength is need reinforcements are added.The reinforcement material used is steel, ribbed steel moulds are created andconcrete is poured into it, this increases the materials properties and becomesa composite. This composite hasconcretes hard and strong properties when compressed but steels flexibilitywhen stretched. The steel used is ribbed to ensure that the concrete sticks toit, this also increases the surfaces area of concrete attached to the steel. vi) Smart materials are materialsthat react to changes or stimulants in their environment. This stimulant couldbe any of the following; heat, light, pressure or electricity.
This change isreversible and can be repeated time and time again. An example of a smart materialis a shape memory alloy, heat is the stimulant that allows a shape to bere-moulded until cold and then once re-heated it returns to its original shape.Piezoelectric materials are smart materials which uses electrical voltage tocause a tiny movement, the piezoelectric materials are used for headphones orcontact sensors for alarm systems.
Thermochromic materials change colourthrough temperature. These are used in baby spoons as the food is cooked, ababy spoon can be put into the food and can indicate if the food is too hot forthe child. Another use of Thermochromic materials are in medication,Thermochromic film can be used to measure people’s temperature.Task 2(M1)Steel is the most common materialused in the automotive industry, Steel is strong and easy to work with alongwith it being cheap and available. Almost every car contains steel as it can beused for various parts such as the roof, chassis, wheels, brakes, exhaust andengines. Steel is available is several different grades and types. The lighterthe steel the more expensive.
Car manufactures use several types of stealthroughout the car with better steel being used where reinforcement is neededfor example the A frame. Steel can be mixed with carbon to create carbon steel,this is lightweight and incredibly strong. It is expensive due to theseproperties being ideal for cars. Type of Steel Iron alloyed with Properties Usage Low Carbon Steel 0.25% Easily Shaped Car Body panels High Carbon Steel 2.5% Hard Car A frame and chassis Aluminium is another common metalused in car manufactures, it is much lighter and stronger then steel and unlikesteel aluminium isn’t susceptible to rust. It is however a lot more expensivethen steel and it is more complex to work with due to this it is not used oncheaper cars, Jaguar and Audi are two manufactures are the two main carcompanies that specialise and have done for a long period in aluminium cars.
Aluminiumcars are now in the prime, due to the need for new electric cars to belightweight, this is essential to get large distance out of a charge. Aluminium back in the day was quickly addedinto the automotive industry due to its reputation in racing cars however theinvention of carbon fibre was quickly following and aluminium is replaced. 2ü CB1ü CB2