7 Oct, 2021 By Johny 2 Comments
What is Carbon Fiber unidirectional fabric?
Carbon Fiber unidirectional fabric is a non-woven form of Carbon Fiber reinforced material, which is characterized in that all fibers extend in a single parallel direction. With this style of fabric, there are no gaps between the fibers, and the fibers lie flat. No cross-sectional weave divides the fiber strength in half in the other direction. This allows a concentrated fiber density that provides maximum longitudinal stretching potential and is greater than any other fabric. It is three times the longitudinal tensile strength of structural steel and one-fifth of the weight density.
Likewise, composite parts made of Carbon Fibers can provide ultimate strength in the direction of the fiber particles. Therefore, composite parts that use unidirectional Carbon Fiber fabric as their exclusive reinforcement provide maximum strength in only two directions (along the fiber direction) and are very stiff. This directional strength characteristic makes it an isotropic material similar to wood.
During the placement of parts, unidirectional fabrics can be overlapped in different angular directions to achieve strength in multiple directions without sacrificing rigidity. In the process of laying the net, the unidirectional fabric can be woven with other Carbon Fiber fabrics to obtain different directional strength characteristics or aesthetics.
The weight of unidirectional fabrics is also very light, even lighter than similar woven products. This allows for better control of the precision parts and precision engineering in the stack. Similarly, compared with woven Carbon Fiber, unidirectional Carbon Fiber is also more economical. This is due to its lower total fiber content and less weaving process. This can save the production cost of parts that seem to be expensive but high-performance.
The biggest advantage of Carbon Fiber unidirectional reinforcement is also their biggest disadvantage. They are not suitable for parts that require large anisotropic strength characteristics (strength in all directions). Composite parts used in automobiles and other multi-dimensional applications that require comprehensive strength enhancement should use different weaving methods, such as plain weave, twill weave, or satin weave.
Another potential disadvantage is that composite parts made of unidirectional Carbon Fibers have a very flat single particle surface. If manufacturers want a beautiful, iconic Carbon Fiber finish, they usually use a single-layer woven fabric as the outermost layer of their layup. For example, bicycle frames are usually made of multiple layers of unidirectional fabrics that are placed in different directions for maximum strength and rigidity, and then made of 3K twill weave Carbon Fiber fabric to have the “iconic” carbon fiber appearance .
Unidirectional reinforcement is ideal for the most important application of strength from front to back. For example, long tubular structures that move only in the forward and backward directions (such as rockets, airplanes, and ships) often use unidirectional Carbon Fiber as a reinforcement material.
Most Carbon Fiber tubes (such as backpacks and bicycles) used in the frame use unidirectional Carbon Fiber because of its light weight and high rigidity. For the entertainment and hobbyist Fmarket, it can also usually be found in model airplanes, drones, model boats, model rockets, bicycles, and entertainment sticks (hockey, lacrosse, etc.).
The progress of Carbon Fiber and resin also makes unidirectional Carbon Fiber reinforced materials more widely used in construction and structural engineering. Due to the excellent strength of Carbon Fiber, it is an ideal substitute for wood or metal in these applications such as bridge or building repair. Carbon Fiber in its multiple composite forms reduces construction time, provides longer durability, and minimizes maintenance costs.
The light weight and stiffness of unidirectional Carbon Fiber are also used in wide turbine blades. Increased stiffness and lighter weight can make the blades longer and thinner. The increased length results in a larger sweep area, and thinner, lighter blades are more sensitive to air flow, both of which provide greater energy output.
Unidirectional Carbon Fiber sleeves are also used in sports other than bicycle frames and sticks. Excellent fatigue resistance, the combination of light weight and rigidity make unidirectional Carbon Fiber very suitable for prosthetic blades, such as those used by Paralympic sprinters. Non-directional Carbon Fiber fabrics are also used in the soles of sprinting and cycling shoes to provide extremely high stiffness and minimal weight in racing applications where energy efficiency is critical.
Fibre Glast currently mainly provides four types of Carbon Fiber unidirectional fabrics, using T700S from Japan’s Toray and IM7 from Hexcel from the United States as raw materials. Less than 3% of the overall structure. Other brands of unidirectional fabrics sometimes have a slight weave in and out of the adhesive. This is not a true unidirectional fabric, because even a slight weave will reduce the maximum unidirectional strength.
All fiber unidirectional fabrics of Fibre Glast are 12 inches wide. This width is easy to use because they can be placed side by side to form a seamless final part. This also makes them easier to store, carry and transport. The carbon fiber used in the fabric has a tensile modulus of at least 33.4 Msi, which has excellent stiffness and a tensile strength of at least 711 Ksi. Generally, the heavier the Carbon Fiber fabric, the more fiber used to increase the thickness, and the higher the strength of the final composite structure. In addition, like other fabrics, additional layers can be added to increase strength.
When using unidirectional reinforcing materials, make sure that the fabric is smooth, with only the Carbon Fiber side facing out to get the most tidy effect. Similarly, spread the resin along the fiber direction-close contact will cause the nonwoven fiber to break away from its binder.
One-way wet laying is the most common, and the vacuum bag process will provide the greatest strength-to-weight ratio. For best results, a vacuum infusion process can be used to achieve the desired resin to fabric ratio. Compared with woven fabrics, because the resin injection process is slower, vacuum injection will be slightly more difficult.