Reinforcing fibres carbon

The lightest structural component for a specified deformation, i.e. strain or deflection, under a specified load is the one with the highest specific modulus. This is calculated as the ratio of the Young s modulus to the density of the material. For comparison purposes in Fig. 11.2 is plotted the specific modulus for several materials, including typical reinforcing fibres. Carbon-reinforced composites possess higher specific modulus when compared against aluminium and steel [1]. 

Commercial grades of polymer may contain, in addition to glass fibre, fire retardants, impact modifiers and particulate reinforcing fillers. Carbon fibre may be used as an alternative to glass fibre. 

Epoxide resins reinforced with carbon and Aramid fibres have been used in small boats, where it is claimed that products of equal stiffness and more useable space may be produced with a 40% saving in weight over traditional polyester/ glass fibre composites. Aramid fibre-reinforced epoxide resins have been developed in the United States to replace steel helmets for military purposes. Printed circuit board bases also provide a substantial outlet for epoxide resins. One recent survey indicates that over one-quarter of epoxide resin production in Western Europe is used for this application. The laminates also find some use in chermical engineering plant and in tooling. 

The reinforcing filler usually takes the form of fibres but particles (for example glass spheres) are also used. A wide range of amorphous and crystalline materials can be used as reinforcing fibres. These include glass, carbon, boron, and silica. In recent years, fibres have been produced from synthetic polymers-for example, Kevlar fibres (from aromatic polyamides) and PET fibres. The stress-strain behaviour of some typical fibres is shown in Fig. 3.2. 

Thermal decomposition of the matrix material offers a simple way of recovering the relatively expensive reinforcing fibres from a fibre-reinforced laminate. The epoxy resin matrix was made to decompose by thermal treatment in air or nitrogen, this treatment allowing the carbon fibres to be recovered without damage. 

The use of reinforcing fillers was examined by Seed Wilson (1980). An alumina-fibre cement had a flexural strength of 44 MPa, while one reinforced by carbon fibre had a flexural strength of 53 MPa. Metal reinforcement has also been examined. Seed Wilson (1980) found that a cement reinforced with silver-tin alloy had a flexural strength of 40 MPa. 

Most significantly, the price per litre varies from about 1 to more than 100 according to the nature of the polymer itself, the formulation of the grades and the inclusion of high-cost reinforcements including carbon fibres and so on. 

Currently, glass fibres are the most widely used, accounting for 95% of the reinforcement fibres consumed by plastics. Aramid and carbon fibres account for nearly all the remaining 5%. 

Reinforcement with carbon and glass fibres moderately improves moduli, as shown in Figure 4.89(b). Note that the load is 14 MPa for reinforced grades and 7 MPa for the neat grade. 

Reinforcement with carbon fibres improves moduli and creep moduli, leading to fair creep behaviour. 

EMS hybrid yarns or Schappe s preimpregnated yarns are a combination of reinforcing fibres (glass, aramid or carbon) and polyamide 12. 

Use a reinforced grade to reduce the wall thickness and consequently the material weight. In ascending order of performance but also of cost, the most-used reinforcements are natural fibres, glass fibres, aramid fibres, carbon fibres. Carbon fibres, if their development leads to a substantial lowering of their cost, could solve many cost problems. 

The production of modern car tyres uses more than 100 raw materials, most of which are based on petroleum products. Tyres consist of natural and synthetic mbber, typically styrene-butadiene (SBR) reinforcing fillers (e.g., carbon black, silica, clay, calcium carbonate) reinforcing fibres... 

Janes, Neumann and Sethna ° reviewed the general subject of solid lubricant composites in polymers and metals. They pointed out that the reduction in mechanical properties with higher concentrations of solid lubricant can be offset by the use of fibre reinforcement. Glass fibre is probably the most commonly used reinforcing fibre, with carbon fibre as a second choice. Metal and ceramic fibres have been used experimentally to reinforce polymers, but have not apparently been used commercially. To some extent powders such as bronze, lead, silica, alumina, titanium oxide or calcium carbonate can be used to improve compressive modulus, hardness and wear rate. 

The recovered lead paste is a mixture of the positive (lead dioxide) and negative (lead sulfate) active materials, small metallic fractions from the grid and other materials that have been added to the battery paste such as carbon black, expanders, and reinforcing fibres. A typical range of components in recovered battery paste is given in Table 15.1. 

Fibre-reinforced polymers (FRP) rebars, usually made of an epoxy matrix reinforced with carbon or aramide fibres, have also been proposed both as prestressing wires and reinforcement. Nevertheless, they are not discussed here, because these applications are still in the experimental phase and there is a lack of experience on their durability. In fact, while they are not affected by electrochemical corrosion typical of metals, they are not immune to other types of degradation. FRP are also used in the form of laminates or sheets as externally bonded reinforcement in the rehabilitation of damaged structures this application will be addressed in Chapter 19. 

ISO DIS 14,127. Composites- -Determination of resin, fibre and void content for composites reinforced by carbon fibre. 

Glass is overwhelmingly the preferred reinforcing fibre in marine applications although aramid (e.g. Kevlar ) and carbon are used where cost permits. Where carbon is used, there is a theoretical possibility of dangerous corrosion cells being set up with exposed carbon fibres electrically connected to metals. This problem is easily avoided. 

Sloan and Talbot [113] reported a study of the anodic exposure of autoclave-cured 30-ply unidirectional AS-4/3501-5a carbon epoxy laminates in unaerated 0.5 M pH 7 sodium chloride at ambient temperature, against a platinum counter electrode. Crack formation was observed at potentials above 600 mV (SCE) at currents as low as 1 pAcm. Discoloration (yellowish brown) of the electrolyte was observed at potentials above 900 mV with both the carbon/Pt and Pt/Pt electrode systems. The reinforcement fibres... 

Attention also needs to be paid to the correct selection of the reinforcing fibre if the maximum longevity of the vessel is to be achieved. When reinforcing fibres are mentioned in the chemical process industry, three kinds are concerned glass, aramid and carbon or graphite. For the manufacture of cost competitive corrosion-resistant vessels for use in industry then the selection may be reduced to just one, glass. 

Primitive reinforced plastics products were known in the 1920s and 1930s, but the more advanced fibre reinforced materials we know today only became significant commercially as structural materials in the 1950s, and even then, the more recent reinforcing fibres such as carbon/graphite, aramid (e.g. Kevlar , Twaron ) and polyethylene (e.g. Dyneema ) fibres were all still completely unknown. The great majority of reinforced plastics articles we use today have been manufactured since 1975. 

Stress-strain curves of typical reinforcing fibres (a) carbon (high modulus) (b) carbon (high strength) (c) aramid (Kevlar 49) (d) S-glass (e) E-glass. 

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