Carbon fiber is a fiber that contains at least 90% carbon and is obtained from the controlled pyrolysis of special fibers. The term graphite fibers is used for fibers with a carbon content of more than 99%.
There are various types of fibers as a precursor to carbon fiber production that have unique properties. The most commonly used background fibers are polyacrylonitrile fibers, cellulosic fibers (such as rayon viscose and cotton), bitumen from coal tar and a special type of phenolic fibers.
Carbon fibers are made by pyrolysis of organic backgrounds in the form of fibers. Heat treatment removes elements such as oxygen, nitrogen and hydrogen and leaves carbon in the form of fibers. Studies on carbon fibers have shown that the mechanical properties of carbon fiber are improved by increasing the degree of crystallization and the orientation of the background fibers and reducing its defects. The best way to achieve carbon fibers with suitable properties is to use the most oriented carbon fiber and maintain it during the stabilization and carbonization processes by applying traction during the process.
Carbon fiber properties:
CIA-colored carbon fibers are odorless and water-insoluble, resistant to acids, bases and organic solvents, non-melting and non-explosive.
There are different types of carbon. In this section, we refer to them:
Carbon fibers can be divided into different groups based on the number of filaments and the Young's modulus and the final strength and temperature of the heat treatment and the type of raw material.
Classification based on physical properties:
Carbon fiber with a very high Yang modulus of more than 450 GPa
Carbon fiber with a high Yang modulus between 350 and 450 GPa
Carbon fiber with an average modulus of Yang between 250 and 350 GPa
Carbon fiber with high tensile strength and low Yang modulus, tensile strength of more than 3 GPa and Yang modulus of less than 200
Carbon fiber with very high tensile strength, more than 5 gigapascals
Classification based on final heat treatment temperature:
Type 1 fibers, heat treatment temperature above 2000 ° C, HM fibers
Type 2 fibers, heat treatment temperature above 1500 ° C, HS fibers
Type 3 fibers, heat treatment temperature above 1000 ° C, low strength fibers
Fabrics of these fibers are produced in 3 types, each of which is considered for a specific application:
1- Plain texture:
Plain weave or Plain weave is the simplest and most common type of weave of carbon fabric, so that the threads of taropod are placed between each other up and down. The fabric is symmetrical and has good dimensional stability. Another feature of this fabric is low sagging of the fabric due to its dense texture.
2- Twill texture:
It is also referred to as twill twist because it is visible on the surface of the fabric. This type of texture is caused by the progress of the warp yarn stages. Twill texture is used more in composite curved surfaces due to its flexibility than plain texture.
3- One-way texture (UD):
By definition, refers to Uni-Directional fabrics that have at least 90% of the fabric weight in one direction (warp or weft). Here, thermoplastic and molten yarn is used in another direction to stabilize them in their position due to heat, softening and attachment to carbon yarns.
Different applications of fibers
Building reinforcement with (FRP), reinforcement and repair of buildings and seismic improvement of structures
Used in the automotive industry. Such as making engine parts, shock absorbers, wheel and steering box accessories, brake pads, racing car hulls, ship hulls, swing springs, etc.
Use in the aircraft industry; Manufacture of satellite components, passenger aircraft interior structures such as carbon seat panels, carbon tables, supersonic aircraft tips, aircraft engine components.