Reinforcing fibres aramid

For the global advanced composites market, the average cost of high-performance fibre reinforcements (carbon, aramid, high modulus polyethylene, boron, R/S/T-glass and some E-glass) is estimated from 5.5 to 6 per kg. This moderate price is due to the decrease in the carbon fibre price. Some grades could fall to less than 10/kg in the short or medium term. 

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%. 

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. 

Superior mechanical properties, including impact strength and resistance to delamination, are claimed for reinforced plastics made from three-dimensional fabrics [1], Other reinforcement forms include continuous swirl mat, designed to have a minimum of fibre ends, and hybrid fabrics containing two different reinforcing fibres, for example, glass and aramid. There are many different ways in which two different fibres can be combined together. 

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. 

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. 

Fibre reinforced plastics. The most wide-spread reinforcement is glass fibre as roving, chopped strand mat, fabric, etc. The most usual matrix materials are unsaturated polyesters and epoxy resins as thermosets. In glass fibre reinforced thermoplastics (e. g. ABS, PA, PPO), the length of the glass fibres is 1 to 3 mm. Other reinforcing fibres are aramide, asbestos, boron, carbon, etc. 

To date, only one class of polymer has been found in which this problem can be overcome and highly successful reinforcement fibres produced. These are the aramld polymers, so-called because they contain both aromatic and amide groups in the molecular chain. Indeed, it is this combination which is the key to their success. Kevlar 49 is currently the most widely used aramid fibre for reinforcement of plastics, and it illustrates the point well. It consists of the polymer poly(paraphenylene terephthalamide) ... 

The reinforcement types which will be discussed are glass fibre, carbon fibre and aramid fibre. Each of these is not a single fibre type but more a family of fibres with a range of properties. Typical properties of a range of reinforcement fibres are given in Table 1.2 The strength and strain figures... 

Glass is predominantly the most important and widely used fibre in reinforced plastics. Other fibres are natural (cotton, sisal, jute), synthetic (nylon, polyester, acetate, rayon), or organic and Inorganic high-performance fibres (aramid. boron, carbon/graphite). 

This is now a specialized area of product development a wide range of formulations has been derived from the small family of basic engineering plastics. The principal additives are the reinforcing fibres (glass, carbon, aramid, etc.), and lubricants such as PTFE, silicone, graphite and molybdenum disulphide, each of which makes a specific contribution. 

ARAMIDS—BRIDGING THE GAP BETWEEN DUCTILE AND BRITTLE REINFORCING FIBRES ... 

This chapter presents in a concise form the relation between the microstructure and the mechanical properties of aramid fibres. At the same time an attempt is made to demonstrate that the rationale behind the design of composite materials can also be employed for the molecular design of the reinforcing fibre itself. 

Figure 10.33 Stress-strain curves of cementitious composites reinforced with aramid (Kevlar) fibres produced by the spray method (after V felton and Majumdar [118]). (a) Effect of 2 years of weathering (b) effect of temperature treatments.

The flexible, tubular hner of a CIPP is typically made of polyester fabric that is a needled, woven or knitted reinforced fibre sheet using carbon, glass or aramid fibres or a combination of both. Depending on its application, the hner is coated with an impervious film such as polyethylene for the transport of drinking water or polyester for gas pipes. Other coatings include urethane and polyvinyl chloride (PVC). The final smooth surface reduces the surface friction and provides an additional corrosion barrier for the pipe. Liner tube sizes range from 100 to 2500 mm in diameter with... 

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. 

Advanced materials can be used in extreme conditions, e.g., high temperatures (> 200°C), severe chemical environments (e.g., polytetrafluoroethylene (PTFE) with concentrated H2SO4). They are often used as a critical component in a workpiece and are frequently reinforced with glass, carbon or aramid (e.g., Kevlar ) fibres. 

Short glass fibre reinforcement the main thermoplastics are offered in such grades. Some short carbon or aramid fibre reinforced resins are also marketed. 

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