Carbon fibre - High Strength Applications
By Dr D M Mohunta
Carbon fibres are a form of pure carbon that has been manufactured by carbonising an organic material to pure carbon in such manner that its mechanical properties are changed without any change in the chemical properties of carbon. That is the characteristic’s with which carbon is identified. In 1960 Richard Millington of H.I. Thompson Fiberglas Co. developed a process (US Patent No. 3,294,489) for producing a high carbon content (99%) fibre using rayon as a precursor. Most carbon fibres have carbon content ranging from 85% to 99%.
When carbon fibres that are about 5-10 micron diameter have be to processed for use the strength of individual fibres is low and have to be processed by bunching them together. This can be achieved by tightly binding them mechanically so that the overall strength required for processing is achieved. However external binding has the issue of interfering with processing, etc.
One possible method is to have temporary or permanent matrix that will hold the fibres together sufficiently so that there is no slippage between fibres and are held together in the required geometry and maintaining the overall strength.
The matrix material can be any polymer or adhesive of sufficient strength. The quantity of Matrix used has to be within certain range or proportion. Lower proportion will not give enough adhesion between the fibres and they would separate. Higher proportion will give a low strength layer between the individual fibres thus reducing the overall strength. The correct proportion is between 17-22% of the carbon fibre. Thus various shapes so created like round, flat, hexagonal are all forms of carbon with high strength .
Carbon fibers processed in this manner retain the properties of carbon as a chemical at the same time provide adequate mechanical strength. The shape of the final product is immaterial to the properties of carbon fiber.
In some applications where high strength is not critical but other properties of carbon fibre are desirable and the cost is a factor higher percentage of polymer matrix have been used.
Carbon fibre is high strength. It is low weight. It is cost-efficient. It is characterized by high stiffness. It is conductive to electricity and is one of the most corrosion and heat resistant materials available for commercial use.
Carbon fibre is versatile. It has the ability to work with an assortment of different materials, including other fibres, plastics, metals, wood, and concrete. It can be manipulated into a variety of forms. It can be dyed, treated, and augmented to meet the requirements of any application.
It is nearly impossible to postulate all of the potential uses of carbon fibre, here are some.
Pultrusion is a cost-effective, continuous process for producing fiber-reinforced composite parts. Characterized by high-strength, high-stiffness, low density, high fiber volume, very low zero void content, locked-in filament alignment, and corrosion resistance, Pultruded Profiles are pre-cured, thick-ply carbon fiber laminates for ideal structural reinforcement applications.
The specific fiber alignment achieved with pultrusion delivers consistently better overall properties in laminates than any other composite manufacturing process. Depending on the end application, these pultruded profiles are typically produced with a thermoset epoxy or vinyl ester resin.
Pultruded profiles are production-ready carbon composites for infrastructure applications, deep sea exploration, wind energy, and other applications benefiting from the unique properties of pultruded carbon fibre parts.
Carbon fibre is the industry standard for carbon fibre wind energy reinforcement. With an excellent balance of strength, stiffness and cost. Carbon fibre allows for more slender blade profile resulting in higher aerodynamic efficiency, lighter, longer, stiffer, and stronger wind turbine blades, overall more efficient wind turbine providing lower levelized Cost of Energy (LCOE) and higher Annual Energy Production.
Renewable energy is being directed into various types of storage batteries that contain Carbon fibre products. Battery can be fully charged and discharged tens of thousands of times without system degradation. Many chemical batteries utilize carbon fibre in the forms of graphitized felt and paper to use as membranes separating conductive solutions and bipolar carbon plates.
The next generation of yachts, cruisers and racing vessels will be lighter and stronger when made with carbon fibre composites. Tough, durable carbon composite material stands up to the extremes of marine environments. The high specific stiffness of carbon fibre lends itself well to use in applications such as masts, hulls and propellers. The end result is better speed and fuel efficiency in end-products and increased cost-effectiveness in the marine manufacturing process.
Carbon fibre fabrics are often utilized in the repair or upgrade of concrete structures including bridges, columns, and beams, provide cost and scheduling benefits through minimally invasive repair methods, and use non-corrosive materials with outstanding fatigue performance. The fabrics are saturated with epoxy and applied to the concrete structure using a wet layup process. The fabrics, in combination with appropriate saturating resins, are referred to as fibre reinforced polymer (FRP) systems.
Carbon fibre have taken sporting goods to the next level of performance. Golf shafts, racquets, skis, snowboards, hockey sticks, fishing rods, bats, and bicycles have all been advanced through carbon fibre reinforcements. The deepest penetration of carbon fibre in the sports equipment can been seen in tennis racket. Players can hit faster ball with the lighter racket and control the ball better with larger area of the racket. In short the applications of carbon fibre are only limited by imagination and technical skills required for its manipulation