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Ah, carbon fiber, that silky black fabric. Rolling this attractive material on complex and composite surfaces is the object of many reducer racing fans. Carbon fiber can not only be simulated in vinyl wraps or textured ABS plastic parts, but it is also an advanced material with specific properties, applications, shortcomings and functions. The term carbon fiber is one of reducing weight, strength, rigidity and aesthetics. Although all these factors have their effects, there are many misunderstandings about this velvety basic material.

The engineering subject of composite materials is a huge field of continuous expansion of research and breakthroughs. We will discuss some basic principles and hope to expand your view of this amazing industrial textile.

Carbon fiber is an industrial textile, which is made from thousands of carbon filaments woven together to make cloth. It is produced in a variety of different weaving methods for different applications, and is only part of a multi-part structural material called a composite material. Composite materials are just things that make up for weakness or strength by combining the qualities of different materials. For carbon fiber, glass fiber, Kevlar and other such textiles, the composite material in question is called FRP (Fiber Reinforced Polymer). In FRP, cloth is used to enhance the structural rigidity of the resin substrate. Resin provides strength to composite materials, while carbon fiber provides structural integrity to otherwise fragile plastics.

How is carbon fiber made?

Carbon fiber, as the name suggests, is a pure element fabric composed of carbon. Starting with carbon and woven cloth will be a daunting task. Textile refineries do not use carbon as a raw material, but start with more complex plastic polymers. This thread is thinner than human hair and has undergone many heat treatments and chemical treatments. The end result of this complex process is that the polymer is reduced to the most experienced form of pure carbon.

Carbon fiber is usually measured and sold according to several standards, weaving pattern, modulus (a measure of the strength of a single filament), fabric weight in ounces per square yard, and tow count (usually in the range of 3,000-12,000) .

What do the different weaving patterns mean?

Unidirectional carbon fiber consists of bundles (tows) of carbon filaments, all carbon filaments are arranged in the same direction, this fabric has no obvious weaving structure. Because there is no weaving, unidirectional carbon fibers need to be fixed together, and diagonal or vertical lines can be used to keep the fabric neat and evenly spaced (but it is not a structural element). Due to its single-dimensional rigidity, unidirectional carbon fiber is not common in motorsports where loads may come from all directions.

http://www.easycomposites.co.uk/

Bidirectional carbon fiber is the most basic basic weaving method. The tows are woven together at right angles to form a square checkerboard pattern that passes through the fabric horizontally and vertically. When using a weaving pattern, the direction of the tow can apply loads on multiple shafts, and the composite material will maintain its stiffness.

Wherever composite materials are used in motorsports, two-by-two twill is the most common carbon fiber weave. This kind of weaving is slightly more complicated than two-way weaving, because the two tows in each direction are woven in a double-up, up, and down manner. The resulting pattern forms a zigzag diagonal pattern on the fabric. Since the 2×2 twill fabric forms a twill pattern with vertical and horizontal (warp and weft) tows, the resulting fabric has extremely strong ductility and can adapt to various complex shapes. When facing the compound curve twill weave, it can fit well without bunching, unfolding or cutting darts.

Similar to two-by-two twill, four-by-four is a weaving pattern that spreads diagonally and consists of four tows in two directions. The resulting weave has a wider distribution than 2 × 2 but provides better surface coverage because the actual points under the weave are farther apart. 4 × 4 effectively has fewer hard seams and is on the composite Or the overhang in the composite easily bends the mold.

http://www.easycomposites.co.uk/

Expanded tow carbon fiber is a very special fabric design, and it is also the rarest one we will discuss. Unfolding the tow means that 3,000 to 12,000 carbon filaments per tow are arranged side by side to form the thinnest ribbon. The traditional tow is composed of many layers of carbon tow into a bundle. The unfolded tow fabric is identified by a large open pattern. A checkerboard pattern of bidirectional carbon fiber, with an unfolded tow structure, may have a square one inch wide.

http://www.easycomposites.co.uk/

Carbon fiber is also available in pre-cured laminate form. If you need blocks, plates, tubes or other shapes, you can buy prefabricated laminates.

Composite laminates can be composed of a variety of materials other than carbon fiber; aramid, metal, metal or polymer foam, honeycomb, etc.

Laminated blocks can be processed into solid composite parts with layered sandstone aesthetics.

As described by Easy Composites, a British material and resin supplier, “Dispersed tow fabrics are becoming more and more popular in advanced composite applications because they have an incredibly flat profile that almost eliminates'through-printing' or precision. The texture of the surface (such as the wing of an airplane). ”

Since the final fabric layer is much thinner, more layers must be used to achieve the same strength. Usually used in applications where aerodynamics is prioritized to strength, the scattered carbon fiber has a unique aesthetic that people either love or hate.

Carbon fiber cloth is only part of the composite material generally referred to in the racing industry. Another important ingredient is the resin that impregnates the cloth and provides the actual stiffness. There are different polymer blends for the resin. The two most common are epoxy resin and polyester resin. Anyone who uses fiberglass to repair surfboards or work in cars knows that resin can be an annoying thing. Volatile organic compounds (VOC) are the fumes that characterize many resins, although there are some chemicals that can avoid these brain damage. The most common adverse effects of using resin without proper personal protective equipment (PPE) are the development of hypersensitivity reactions and allergies. This situation can become so serious that we have heard anecdotes about people not being able to live in the same room with resin.

http://www.easycomposites.co.uk/

Epoxy resin is the most common general structural resin. Like almost all resins, it is usually a two-part solution of resin and catalyst. The reaction start time will vary, but it will vary with environmental conditions. The pot life (working time) is generally about 5 to 30 minutes. Generally speaking, heat will always accelerate the curing process, but it usually takes 24 hours to fully cure. Compared with polyester, epoxy resin is a stronger resin, but it requires some patience.

Polyester resin is a fast-curing, cheaper alternative to epoxy resin. According to easycomposites.co.uk, it is usually used in situations where structural integrity degrades aesthetics. "However, in some cases, the structural properties of the laminate are less important, while properties such as appearance, UV stability, and cost Is a higher priority."

http://www.easycomposites.co.uk/

Some carbon fiber cloth may be pre-impregnated with a resin solution and rely on heat as a catalyst. Pre-impregnated cloth is used in most industrial composite environments because it is easy to apply (usually an adhesive backing), and there is minimal confusion by mixing resin and applying wet fabric layer after layer.

http://www.easycomposites.co.uk/

Prepreg is also the material of choice for weight-conscious industries such as the aerospace market, because most of the weight of composite materials is in the resin, not the cloth. Carefully and evenly immerse the cloth with the least necessary resin, it can be used to create the strongest and lightest combination.

The stippling motion is used together with the paintbrush to apply resin to the cloth in the mold.

Traditionally, the small part is wet, with a female mold, and a plug is created (that's another matter). Then put the dry cloth into the mold. Apply the resin with a paint brush until the cloth is completely "soaked" or saturated. The subsequent cloth layer is placed on the first layer, paying attention to the alternate weaving direction, 45 degrees in both directions, and 90 degrees in the twill weave. If the fabric layers do not alternate in the weaving direction, the final part will be stiffened along one axis while the other is over-strengthened.

Vacuum bagging helps remove air bubbles and excess resin in composite parts. http://www.easycomposites.co.uk/

Depending on the thickness of the part and the number of saturation layers required for strength, the excess resin will be squeezed out, just as you would remove water from a windshield. Then vacuum bag the parts and apply low pressure to the contents to suck all the resin into any existing voids to remove tiny bubbles and any excess resin.

An autoclave is an oven used to cure composite parts.

In some cases, these processes will be reversed. The dried fabric is vacuum bagged in a mold and then coated with resin. This method reduces waste and confusion. The last step is heating. A pressurized oven called an autoclave is used to bake the parts and fully cure the resin.

Although most of us cannot use professional equipment, vacuum bagging and autoclave baking are optional for casual parts that do not need to meet specific structural requirements.

http://www.easycomposites.co.uk/

Carbon fiber has gained momentum in the manufacture of various automotive products. In the aftermarket, carbon fiber is most commonly used for decorative parts. Carbon fiber body parts, trims, etc. give a high-performance appearance. The functional applications of carbon fiber components range from automobiles to marine and aerospace applications.

Carbon fiber is used to make safety equipment such as racing seats, drive shafts, helmets, and head and neck restraints (HNR), and even composite spring technology is being applied to suspension systems.

Carbon fiber is also woven into a round tube to improve torsional strength.

Carbon fiber is not a universal solution

The appeal of carbon fiber is so strong for many people that it has a tendency to be misused in applications where metal alloys are still the best solution. Carbon fiber, resin, in particular, when carbon is selected as the material, it is necessary to carefully evaluate high-heat localities, heat shields, exhaust components or other engine components before manufacturing. High heat resins exist, but their applications are still limited.

Impact damage is the persistent fragility of composite materials.

Carbon fiber has the slogan "lighter than aluminum, stronger than steel". Although this statement has its place, it is important to understand that this is a reference to tensile strength, not toughness or hardness. In engineering terms, "toughness" refers to the technical term for wear resistance, because this composite material is layered glass fiber reinforced plastic with low impact resistance. Even the slightest tip impact can cause the material to delimit and eventually fail. For these reasons, carbon fiber cannot manufacture anti-skid plates, suspension parts, or other exposed high-stress parts that are durable or can withstand multiple impacts.

Carbon is conductive! Pure carbon transfers heat by itself very efficiently. For example, a car hood made of virgin carbon fiber can heat up to hundreds of degrees very quickly in the sun. Ultraviolet rays can have a devastating effect on composite materials-yellowing or resin cracking, and warping is common. Many aerospace applications of carbon fiber are painted bright white because the heat generated by ultraviolet rays can damage the airframe, change aerodynamics, and have other negative effects on the structure of the aircraft.

Carbon fiber cloth is conductive. Photo courtesy of SAE.

Carbon fiber is conductive. The electrical conductivity of plastic matrix composites can be confusing, but the pure carbon cloth passing through it provides a path for electrical conduction, even if it is impregnated with insulating polymer. When using carbon as the surface of electronic equipment or installing a cooling fan shield, make sure that the ground does not pass through the carbon. Personal anecdote... We witnessed the owner of the Geiser Trophy Truck pre-runner almost caught the engine on fire because he didn't believe that carbon fiber is conductive and resin fire is irrelevant.

If you have ever used glass fiber filaments in your skin, you will know how irritating these invisible fragments are, but carbon fiber is much worse! Avoid touching rough edges and chopped fibers with bare hands.

Carbon fiber cloth must not be folded and can only be placed on one character. http://www.easycomposites.co.uk/

When ordering carbon fiber fabric, it is important to ensure that it is shipped in rolls, such as wrapping paper. Flat-folded carbon fibers can crimp and destroy the structural integrity of the crimped filaments. It is recommended to be careful when handling and keep the fabric clean and free of any dust or oily fingerprints to ensure the best laying. It is normal to mix resin in small paper cups, but be careful not to mix resin in waxed cups. Wax can interfere with the adhesion of the resin and the curing of the resin. Resin curing is an exothermic reaction, which means that a lot of heat is generated as a by-product of the chemical reaction. If you mix a large amount of resin, make sure to keep the excess resin away from flammable materials at the beginning of the resin, otherwise it may cause a fire.

We haven't even covered a large amount of knowledge base in this article, but we hope this overview helps broaden your understanding of carbon fiber. If handled properly, it is an incredibly versatile and strong material, but if used incorrectly, it can cause misalignment. Home production of simple parts is not difficult, but it is estimated that the cost of raw materials is several times that of glass fiber. Consider your project, goals, and budget, and then decide whether the carbon fiber structure is the right choice, or do you just want to improve the aesthetics?

Kevlar and carbon fiber colored cloth are a way to decorate your composite parts. http://www.easycomposites.co.uk/

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