IB DT: Topic 4.2f: Composites

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what is a composite material?

a combination of two or more materials that are bonded together to improve their mechanical or physical properties. composites can be investigated as a whole but breaking them down into three key areas is most useful to achieve a detailed understanding - form, process and composition

how can textiles form part of a composite material?

fibres can be spun into filaments, string or rope, used as a component of a composite material or matted into sheets to make such products as fabrics, paper or felt. synthetic fibres can be produced very inexpensively and in large quantities, compared with natural fibres.

what can fabric fibres be combined with to form composite materials?

woven fabric fibres and other reinforcements are used in conjunction with resins (the matrix) to produce composite materials which combine the strengths and overcome the weaknesses of materials to produce very strong materials.

how can glass form part of a composite material? what can glass be combined with?

glass is generally made into sheets. when glass is laminated it becomes a composite because there is an interlayer between the glass sheets made from PVB (polyvinyl butyral). when the glass is shattered the interlayer keeps the glass layers bonded, preventing the glass breaking up/fragmenting.

how can metals form part of a composite material?

generally in particles. particle reinforced composites are less effective than fibre reinforcement. generally achieves gains in stiffness, strength and toughness.

what are the two categories of constituent materials?

matrix and reinforcement. the matrix for carbon fibre is an epoxy resin which surrounds and supports the reinforcement materials

how is carbon fibre produced industrially?

carbon fibre sheets and epoxy resin are cured in a moulding device called an autoclave with heat and pressure. this enables shapes to be made with very tight tolerances. on a more bespoke level, manufacturers use a hand-layup process - a mould is requires but the carbon fibre weave is layered between coats of epoxy resin.

what applications is woven carbon fibre useful for?

anything requiring a high strength-to-weight ratio

how is hand lay up different to spray lay up?

hand lay up is an open moulding method suitable for making a wide variety of composite products. production volume per mould is low and is feasible to produce substantial production quantities using multiple moulds.

spray lay up is an open mould similar to hand lay up, except it uses a chopped laminate with good conformability and is sometimes faster than hand lay-up in moulding complex shapes

what is pultrusion?

a continuous process for manufacture of composite materials with constant cross-section. the term combines pull and extrusion. the raw material is often a liquid resin mixture (fibres saturated with a liquid polymer), which is then pulled through a heated steel forming die using a continuous pulling device.

how is concrete made?

main mix: cement, aggregate (stones), water

additives and reinforcements are added to the material to achieve the desired physical properties of the finished material. when these ingredients are mixed together, they form a fluid mass that is easily moulded into a shape. over time, the cement forms a hard matrix which binds the rest of the ingredients together into a durable material with many uses.

what is engineered wood?

• composite wood, man-made wood, manufactured board.

  includes a range of derivative wood products which are made by binding or fixing the strands, particles, fibres veneers or boards of wood together with adhesives or other methods of fixation to form composite materials.

what is cross-laminated timber?

a versatile, multi-layered panel made of lumber. each layer of boards is placed cross wise to adjacent layers for increased rigidity and strength.

what is plywood?

a sheet material manufactured from thin layers of wood veneer that are glued together with adjacent layers having their wood grain rotated up to 90 degrees to one another. used in many applications that need high-quality, high-strength sheet material. this means resistance to cracking, breaking, shrinkage, twisting and warping

what is a particle board/chipboard?

an engineered wood product manufactured from wood chips, sawmill shavings or even sawdust, and a synthetic resin or other suitable binder which is pressed and extruded. less expensive than plywood, denser, lighter, more uniform, but not as attractive.

what is fibreglass (glass-reinforced plastic)?

a composite material or fibre-reinforced polymer made of a plastic reinforced by fine fibres made of glass. it is really strong compared to its weight, corrosion resistant, water resistant.

what is kevlar?

a high-strength material that was first commercially used in the early 1970s as a replacements for steel in racing tires. now used in sporting goods. natural toughness helps to allow fabrics and threads to stand up to repeated abuse. kevlar helps to minimise vibration transfer and can sustain deformation without breaking.

what is carbon reinforced plastic (carbon fibre)?

an extremely strong and light fibre-reinforced plastic which contains carbon fibres.

expensive to produce, commonly used wherever high strength-to-weight ratio and rigidity are required. the binding polymer is often a thermoset resin such as epoxy resin.

what is laminated veneer lumber (LVL)?

an engineered wood product that uses multiple layers of thin wood assembled with adhesives. offers several advantages over typical milled lumber: made in a factory over controlled specifications. stronger, straighter and more uniform - less likely to warp, twist, bow or shrink. easy to form using cad/cam, curves and arches easy to make, dimensions are limitless.