AFRP Aramid Fiber
Aromatic polyamide, or Aramid Fiber for short (UAW code), was first introduced by DuPont in the early 1960s under the Nomex brand. The main feature of this product was its High Heat Resistant. This product is used in the preparation of protective clothing, air purification, thermal and electrical insulation and as an alternative to fireproof cotton. DuPont’s director of research and development at Nomex was Dr. Wilfred Sweeney, a Scottish scientist.
Further research on Aramid Fiber at DuPont by Polish-American chemist Stephanie Kulk led to the development of the para-aramid Kevlar in 1973. Aramid fibers are now known in the industry as the Kevlar brand. Also known as AFRP fibers.
AFRP unidirectional fabric is applicable in various forms of reinforcement for its excellent mechanical properties. This Aramid Fiber has the properties of resisting bend, shearing, compression seismic and wind, durable usage, controlling extension of fissure and deflection and increasing the ductility of structures.
Excellent chemical stability of Aramid Fiber unidirectional fabric can prevent the reinforced and repaired structures from erosion hazard caused by acid, alkali, salt and ultraviolet. Aramid fiber unidirectional fabric is strongly adapting to climate change such that fire retardant coating can easily cover the reinforced structures to prevent fire. In comparison with traditional means aramid fiber unidirectional fabric has unique advantages that it can strengthen the adaptation of structures against severe external environment to prolong the life of the structure; and the light weight and high strength of aramid fiber unidirectional fabric will add almost no volume and weight to the structure.
The general definition of aramid is a product in which a fibrous material is formed in which a long chain of synthetic polyamide with at least 85% of the aramid bonds attached directly to the two aromatic rings.
Various Kevlar fibers are used in industry today. For example, Kevlar 49 is used to strengthen and reinforce concrete. Kevlar 29 is used for applications that need to have a very high impact resistance (such as bulletproof vest).
Kevlar fibers are lighter than carbon fibers and glass fibers and have the highest tensile strength to weight among them. This fiber is approximately 43% lighter than glass fibers and 20% lighter than carbon fibers. The low specific gravity and high tensile strength of these fibers result in a tough, impact resistance structure with a stiffness of about half the carbon fiber. Bulletproof vest is one of the most successful applications of aramid fibers.
The tensile strength of Kevlar fibers is approximately 55% of the tensile strength of glass fibers and its shear strength is 180% of glass fibers. The tensile strength of Kevlar fibers is also 10% lower than that of carbon fiber. Although Aramid Fiber has elastic behavior under tensile forces, they have nonlinear behavior under compressive stresses and reach the yield point at a compressive strain of 0.55-3%.
Kevlar polymers have properties such as high melting point, excellent thermal stability, flame resistance and insolubility in many organic solvents.
Ultraviolet light destroys aramid fibers. The amount of this damage depends on the thickness of the Kevlar fiber, because the Kevlar fibers have a protective role and the destruction of the top layers prevents the destruction of the underlying layers. This problem is less important in composite structures. Because the matrix or composite resin plays a role in protecting the fibers to some extent. Also, by adding UV absorbers to the resin, the above problem is greatly reduced.
In terms of chemical resistance, most organic solvents have little effect on Kevlar fibers and most aqueous solutions of salts do not. But strong acids and bases affect Kevlar fibers at high temperatures or in high concentrations.
Aramid and Kevlar fibers have a matte yellow color and are similar to the carbon and glass fibers used in composites in various forms such as yarn, spun fibers, fabrics and short fibers offered by Afzir Company in the Iranian market. It should be noted that cutting aramid fibers is difficult to do with conventional cutting tools and requires special cutting tools.
Regarding the market for the sale of Kevlar fibers and the price of Kevlar fibers in Iran, it can be pointed out that the price of aramid fibers is high and is preferably used in the manufacture of materials such as bulletproof vests instead of building retrofitting operations.
Aramid fiber unidirectional fabric could be operated easily with small electric tools and in a limited space. This is an advantage that traditional technology cannot meet. Shortening the work stoppage; greatly reducing the economic losses and social influence for its fast speed, shortening construction period and operation in the continuous traffic vibration condition are beneficial advantages gained from application of aramid fiber unidirectional fabric.
As to the flexibility of Aramid Fiber unidirectional fabric, its noteworthy that this fabric could be closely connected to the structure, with no change in shape of the structure and suitable for the coating so that, the reinforcement traces will be invisible.
- The ratio of tensile strength and modulus to weight of Kevlar fibers is excellent.
- The resistance of Kevlar fibers to impact is very high.
- The fatigue resistance of Kevlar fibers is good.
- The resistance of these fibers to acids and bases is good.
- The resistance of Kevlar fibers to corrosion failure is excellent. Kevlar fibers are not sensitive to cracking and have high resistance.
- Kevlar fibers are resistant to organic solvents such as fuels and emollients.
- Vibrational energy dissipation and vibration damping in aramid fibers is good.
- Kevlar fibers can be used continuously up to 180 degrees Celsius.
- In case of fire, Kevlar fibers have Self-extinguishing with low smoke properties
- Apply on structural elements in retrofitting & strengthening projects
- Manufacture of military bulletproof vests
- Construction of military armored vehicles
- Uniforms for police officers and security guards
- Firefighting suits
- Car racing drivers’ uniforms
- Fire hats
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Frequently Asked Questions
What are Aramid Fibers?
Aramid Fibers are a type of synthetic fiber made from aromatic polyamides. Aramid Fibers were the first organic fibers with sufficient tensile strength and modulus to be used in advanced composites. These fibers are very resistant to heat and high temperatures. In addition, their tensile strength is almost five times that of steel. At the same time, it has a very low weight. For this purpose, it is used in various applications.
How are Aramid Fibers compared to carbon fibers?
The main difference between carbon fiber and Aramid Fibers is that aramid fiber is hard but carbon fiber is brittle. In addition, carbon fiber has a higher strength than aramid.
How are aramid fibers compared to glass fibers?
The tensile strength of aramid fibers is almost the same as the tensile strength of glass fibers. But the modulus of aramid fibers can be about twice that of glass fibers. In addition, glass fibers are heavier than heavy aramid fibers. In order to obtain a strength equal to the strength of glass fibers, half of the aramid fibers can be used to obtain the strength of the glass fiber sample.
What are the different trade names of aramid fibers?
Aramid fibers are available in different brands. Different brand names of Aramid Fibers are: Kevlar, Technora, Tawron, Nomex and ...
What are the different types of Aramid Fibers?
Aramid fibers are available in two different types, meta aramid and para aramid. Meta-aramid fibers have excellent thermal, chemical and radiation resistance. For this purpose, metaramides are used in fire-resistant textiles. Para-aramid fibers have a higher strength than meta-aramid fibers. For this purpose, para amides are used to strengthen civil structures.
What are the benefits of aramid fibers?
Aramid Fibers have good properties such as high strength, good abrasion resistance, good resistance to organic solvents, non-conductive, no melting point, low flammability, good integration at high temperatures, high yang modulus, etc.
What are the disadvantages of aramid fibers?
Disadvantages of Aramid Fibers include low moisture absorption, low adhesion to resins, sensitivity to ultraviolet rays and acids, relatively high cost, and so on.
What are the uses of aramid fibers?
Aramid Fibers are commonly used as reinforcing fibers for polymer-based composites. Other applications of aramid fibers include the manufacture of protective clothing, sails, car parts, aircraft fuselages, boat hulls, fiber optic and electromechanical cables, military applications, aerospace, ballistic protection applications such as bulletproof vests, etc...
With what resins are Aramid Fibers used?
Aramid Fibers are compatible with epoxy resin, vinyl ester resin and isophthalic polyester resin. But the best adhesion and best performance is provided by epoxy resin.