Carbon fiber is a super strong material that is extremely lightweight. It is five times as strong as steel, two times as stiff, yet weighs about two-thirds less. Carbon fiber is basically very thin strands of carbon (even thinner than human hair). The strands can be twisted together, like yarn and then be woven together, like cloth. To make carbon fiber take on a permanent shape, it can be laid over a mold and coated with a stiff resin or plastic. Carbon fiber can also be defined as a fiber containing at least 92 wt % carbons.knitting fair introduce to you.
Carbon fibers are a new breed of high-strength fiber. It came into existence in 1879 when Edison took out a patent for the manufacture of carbon filaments suitable for use in electric lamps. However, in the early 1960s, when there was a need f of the aerospace industry – especially for military aircraft – for better and lightweight materials, successful commercial production started.
In recent decades, carbon fibers have found wide usage in aeronautics, athletic performance, automobiles, building structures and, of course, musical instruments. Carbon fibers are used in composites with a lightweight matrix.
Carbon fiber composites are ideally suited for applications where strength, stiffness, lower weight, and outstanding fatigue characteristics are critical. They are used in the occasion where high temperature, chemical inertness, and high damping are important. They have been extensively used in composites in the form of woven textiles, prepregs, continuous fibers/roving, and chopped fibers. The composite parts can be produced through filament winding, tape winding, protrusion, compression molding, vacuum bagging, liquid molding, and injection molding.
There are two most important precursors in the carbon fiber industry are polyacrylonitrile (PAN) and mesophase pitch (MP). The structure and composition of the precursor affect the properties of the resultant carbon fibers significantly. Although the essential processes for carbon fiber production are similar, different precursors require different processing conditions in order to achieve improved Performance.
Examples of Application
Aerospace – flights, rockets, satellites
Environment and Energy-related – wind power blade, tube power tank, battery charging flywheel, fuel cell, tidal power blade, the electric cable core
Auto-mobile – hood, roof, propeller shaft, body panel for the bus, compressed natural gas tank
Industrial use- the body of trains, x-ray top panel, pc housing, robot hand for liquid crystal panel, bridge pier reinforcement
Sports material – fishing rod, bicycle, hockey stick, racket, golf shaft.
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Benefits of Carbon fiber
The potentially low-cost carbon fiber composites will be in a position to provide enormous advantages to a number of technologies for current and future everyday life applications, including a number of advanced technologies that are not currently commercially feasible. Lightweight components for automobiles, buses, trains, aircraft, ships, and applications including lightweight panels and load-bearing structures could result in weight savings, leading to a major saving in the nation’s and world’s energy consumption.
Low-cost carbon fiber is a national goal towards accomplishing a number of manufacturing technological breakthroughs.
Difficulties of Carbon Fiber
Cost is the main hurdle carbon fiber will have to overcome before it can provide a viable energy solution.
The second hurdle is waste disposal. When a typical car breaks down, its steel can be melted and used to construct another car (or building, or anything else made of steel). Carbon fiber can’t be melted down, and it’s not easy to recycle. When it is recycled, the recycled carbon fiber isn’t as strong as it was before recycling.
Lack of high-speed composite fabrication techniques.
Manufacturing of Carbon fibers
Carbon fiber is a super strong material that is extremely lightweight. Carbon fibers generally have excellent tensile properties, low densities, high thermal and chemical stabilities in the absence of oxidizing agents, good thermal and electrical conductivities, and excellent creep resistance. Therefore Carbon fiber is enabling advancement in aeronautics, athletic performance, automobiles, building structures and, of course, musical instruments.
Carbon fibers are manufactured by a controlled pyrolysis of stabilized precursor fibers. First Oxidization process is done wherein the stabilization of precursor fibers at about 200-400 °C in air is done. Then carbonization is done wherein these fibers which are stabilized and infusible are treated at a high temperature of about 1,000 °C in an inert atmosphere to remove hydrogen, oxygen, nitrogen, and other non-carbon elements.
Then graphitized is done on those carbonized fibers at an even higher temperature up to around 3,000 °C to achieve higher carbon content and higher Young’s modulus in the fiber direction. The properties of the resultant carbon/graphite fibers are affected by many factors such as crystallinity, crystalline distribution, molecular orientation, carbon content, and the number of defects. The resulting carbon fibers are then post-treated to improve their adhesion to composite matrices.
Source: textiles school
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Physical properties of warp yarn are improved by incorporating oligomer resin into the yarn interior at the size box. These improvements yield benefits at each step of the fabric formation process from size box to the woven greige fabric. Warp sizing technology has been in a period of stagnation following the introduction of synthetic polymers into size formulations nearly 60 years ago. As noted in the following Warp Sizing: knitting fair us A Brief History, abrasion-resistant surface barriers may have reached optimum performance in sizing.
Warp Sizing: A Brief History
Around 1740, increases in woven fabric production were anticipated with the development of the mechanical loom. Optimism was quickly tempered by severe loom abrasion of machine direction yarn. Loom abrasion of yarn prevented any realistic production expectations to be achieved. This problem inspired the adoption of a concept from the coatings industry and a protective surface barrier was applied to machine direction yarn. Starch provided an economical and effective barrier film which could be easily removed from loom state fabric after weaving. Machines were soon developed to apply this barrier coating to yarn.
Following the introduction of synthetic fiber/cotton blends, poor adhesion of starch size formulations forced adoption of high molecular weight, and higher cost, synthetic polymers into warp size formulations. This was the last major change in warp sizing. The barrier concept has been refined to a point where it is now considered to be “the best that we can do”. Synthetic polymer/starch blends are now the primary choice in spun yarn size formulations and warp sizing has now become an outlier in our industry. Thankfully, this attitude has not reached acceptance on either side of the size box.
Consider the Warp Size Process
More is involved in applying a barrier coating to warp yarn than a simple “painting process”. The slasher requires significant capital, large manufacturing space, continual preventative maintenance, and constant personnel training. Application of abrasion barrier and lubricant to warp yarn have been the sole function of the slasher.
Improving Yarn Background
Investigation of oligomer resins was initially proposed for potential adhesion improvement of high molecular weight polymer size films to yarn. All trials were performed in operating mills with no changes to established practices. Results were very confusing. Evaluations with oligomer resins provided benefits far beyond any improvements in adhesion by the barrier film. Results did not fit into any logical interpretation which could be attributed solely to a surface barrier coating. Every step in the process from size box through greige fabric demonstrated benefits. Oligomer resin technology appeared to be adding more than improving adhesion to the size film to the most important component of the entire process.
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Proposed Mechanism
An article presented in this forum in 2019 provided a high magnification cross-section photomicrograph of 40’s Ne ring-spun cotton yarn. This cross-section photo illustrates the presence of micron size voids typical present between fibers in spun yarn. Empty spaces between fibers in spun yarns are determined by the limit of fiber cohesion and are stabilized by anionic repulsive forces on adjacent fiber surfaces.
As warp yarn enters the size formulation, water and oligomer resin are carried throughout the yarn bundle. Oligomer particles immediately are attracted to fiber surfaces and properties of the resin overwhelm any anionic character present. Elimination of repulsive forces on fiber surfaces permits a more intimate fiber arrangement within the yarn bundle. The result is a more compact substrate and the resulting increase in fiber cohesion within the yarn bundle. Increases in fiber cohesion are reflected in the physical properties of the yarn substrate.
Verifying the Proposed Mechanism
Improvements in physical properties of only the yarn itself cannot be measured directly in sized yarn. Comparisons of hard yarn with and without oligomer resin provide useful data but do not rule out the barrier film as the basis of improvement. Two alternative methods were investigated to detect yarn changes resulting from oligomer resin. Addition of oligomer resin in the final rinse of a mock dye procedure provided improvements in both tensile and elongation.
A second approach was conducted to identify potential improvement in yarn properties by spraying oligomer resin directly on fiber. The test was conducted at the USDA facility in New Orleans, Louisiana. A 540 lb bale of Pima cotton (supplied by Buhler Yarns, Jefferson, GA) was crudely sprayed with 8 lb of a 15% active dispersion. The treated cotton fiber was then processed through the USDA production unit to produce 30’s Ne ring spun yarn. No processing problems were noted throughout the entire process. After spinning, control and treated yarns were sent to Gaston Textile Technologies in Belmont, NC for evaluation.
Source: textiles school
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