Composite Materials.pptx

8/14/2019 Composite Materials.pptx

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Jia Xiang, Marvin,

Tathva Ian, Pu Yun,

Sherwin Diva


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Composite materials (composition materials) arematerials made from two or more constituent materials

with significantly different physical or chemicalproperties, that when combined, produce a material

with characteristics different from the individualcomponents. The individual components remain

separate and distinct within the finished structure. The

new material may be preferred for many reasons:common examples include materials which are

stronger, lighter or less expensive when compared totraditional materials.


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Basically almost everywhere.


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The earliest composite materials were strawand mud combined to form bricks for buildingconstruction. This ancient brick-making

process was documented by Egyptian tombpaintings. Wattle and daub is one of the oldestman-made composite materials, at over 6000years old. Concrete is also a composite

material, and is used more than any other man-made material in the world. As of 2006, about7.5 billion cubic metres of concrete are madeeach yearmore than one cubic metre forevery person on Earth.


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Woody plants, both true wood from trees and suchplants as palms and bamboo, yield natural compositesthat were used prehistorically by mankind and are stillused widely in construction and scaffolding.

Plywood 3400 B.C. by the Ancient Mesopotamians;gluing wood at different angles gives better propertiesthan natural wood

Cartonnage layers of linen or papyrus soaked in plaster

dates to the First Intermediate Period of Egypt c. 2181-2055 BC and was used for death masks


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Papier-mch, a composite of paper and glue, has beenused for hundreds of years


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Spray-up

Wetlay-up

Compressionmolding

IInjectionmolding

Vacuuminfusion

Filamentwinding


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Wet lay-up

The component is built up in a mould by applying several layers of reinforcementand wet resin, which is distributed by a roller, until the desired thickness is

achieved. The resin is then cured, using applied heat if necessary, to produce thefinished component.

This process is widely used in the marine industry to prepare glass-fibrereinforced polyester resins. Material costs are relatively low and the process isvery flexible. However, it is labour intensive and suffers the drawback of highstyrene emissions.

Spray-up

A spray gun is used to apply chopped fibre reinforcement and wet resin to amould until the desired thickness of material is built up. The resin is then cured.The process is faster and cheaper than wet lay-up, but mechanical properties arelower.

The process is typically used for large, relatively simple structures such asbathtubs, boat hulls and storage tanks.


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Compression moulding

A charge of fibre and resin, either sheet moulding compound or bulk mouldingcompound, is placed in a preheated mould, which is then closed, and held under

pressure until the resin is cured. The process can generate a Class A surfacefinish, and the similarity to the stamping process used for sheet metals has led toapplications in the automotive industry.

The high investment in heated tooling means that the process is only suitable formedium to high volume production.

Injection moulding

Bulk moulding compound is heated and injected into a heated mould, where itis held under pressure until the resin has cured. The process is used forrelatively small components for which a short cycle time can be achieved. The

high cost of tooling means that the process is suitable only for medium to highvolume production.


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Resin transfer moulding (RTM)

A fibre preform or fabric is placed in a heated mould. Reactive resin is mixed andinjected into the mould under pressure. Pressure is maintained until the resin has cured

and the part is removed. The process is suitable for complex, highly-loaded parts, and isused in a wide range of industries. Vacuum assisted resin transfer moulding (VARTM)is a variant of the process in which vacuum is applied to the closed mould, allowingresin to be injected under low pressure. The loads on the tooling are therefore lower,

allowing cheaper, larger tools to be used to fabricate large structures such as boat hullsor wind turbine blades. A further variant is structural reaction injection

moulding(SRIM). This uses highly reactive resins such that the mould does not need tobe heated to cure the resin, although it often is heated in order to reduce cycle time.

Vacuum infusion

Vacuum is used to cause a low viscosity resin to impregnate a fibrous preform. Most

commonly, the resin is caused to flow over the surface of the preform, and then toimpregnate through the thickness, minimising the distance the resin must travel

through the preform. The process is well-suited to large components such as boat hullsor wind turbine blades. The tooling does not have to carry substantial loads during the

process.


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Filament winding

A fibre tow is passed through a resin bath and applied, under tension, to a convexmandrel. The mandrel is rotated and the fibre release is moved to lay down fibres

in the desired geometry until the required thickness is achieved. The composite isthen allowed to cure, using elevated temperature if necessary. The process can beautomated for high volume production, and is used for tubular structures such as

pipes and driveshafts, as well as more specialised structures such as pressurevessels or monocoque bicycle frames. In the last two applications, the mandrel will

remain inside the component. In a variant of the process, pre-impregnated fibre

tows or slit prepreg can be used, removing the need for a resin bath, but requiringa high-temperature curing stage.

Pultrusion

Fibre tows are taken from a creel and fed through a resin bath, before being pulled

through a heated extrusion die, which cures the resin to produce an extruded partwith axial reinforcement and constant cross-section. Applications include gratings,ladder sections, bridge parts and handrails. The process can be automated and uses

low-cost raw materials, making it suitable for high volume


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Composite Materials.pptx

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