A Guide to Understanding Carbon Fiber Weaves and Fabrics

Interesting | September 19th, 2014 by 0
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Carbon fiber originated for aerospace use, but as it has become more usable this material expanded into the automotive industry.  It has several properties that …

Carbon fiber originated for aerospace use, but as it has become more usable this material expanded into the automotive industry.  It has several properties that make it a superior product for so many automotive applications.  Properties such as high rigidity, tensile strength, chemical resistance,  temperature tolerance, and with a low weight and thermal expansion.

Carbon Fiber is a material that consisted of thousands of carbon atom fibers in diameters of 5 to 10 micrometers.  In order for RW Carbon to produce carbon fiber products like front lip spoilers, rear diffusers, trunk spoilers, trunks, hood and many more, the carbon atom crystals must be bonded together in a symmetrical and parallel pattern.  This alignment gives the carbon fiber its strength and the ability to be lightweight.  Thousands to millions of these carbon fibers are bundled together to form carbon fabric.

From there a mold must be made of the desired aero piece.  In order to form your favorite carbon fiber parts and accessories, resin must be added to the carbon fabric and then molded.  When a perfect mixture/ratio of carbon fabric and resin is used the parts become extremely rigid and take on a very high strength-to-weight-ratio.

Strength- to-Weight-Ratio:

Every carbon fiber aero part that is designed has its own special number of layers of fibers to create a perfect ratio of strength, weight and stiffness.  This is why carbon fiber is so limitless when it comes to the design aspect.  Metal on the other hand is more limited on the shape it can provide.  Carbon fiber composites typically weigh a quarter of the weight of steel, but has the same amount of rigidity, making it 4 times as stiff on a weight-to-weight basis.

To many potential carbon fiber buyers, determining why a particular type of carbon fiber is used over another can be quite confusing. Lets first break down the different categories of Carbon Fiber Woven Fabrics.

1. 2×2 Twill Weave

The 2×2 twill weave is by far the most common carbon fiber fabric used in the automotive industry. This fabric type follows a distinct diagonal pattern. When you think about a 2×2 carbon weave look at it as a pattern that goes over two intersecting warps and under two (hence why it is called 2×2). This makes the fabric more pliable and looser. That means it can be applied more easily because it can be stretched to curves and contours with fewer complications. However, this also means the applicator needs to handle the weave more carefully than a plain or 1×1 weave as it is simple to leave slight distortions in the weave.

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2. Plain (1×1) Weave

The plain or 1×1 weave is the second most used fabric type in the auto industry. As you would expect it is given its name (1×1) because it looks more like a checker board where the weave pattern goes up one and down one. Plain weave is then a tighter knit fabric and is easier to handle without making any distortions. On the down side the tighter weave makes it more difficult to drape the fabric over the mold; making this type a second favorite choice for most manufacturers.

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RW Carbon offers both carbon fiber weaves in certain items we sell.  The majority of products only come in 2×2 twill weave but for our BMW M3 and M6 owners we offer 1×1 or 2×2 which give them the option to match their carbon fiber roof.

Other or Less Common Weaves

The majority of carbon fiber parts and accessories are made using these two types of weaves mentioned above. However, there are others out there such as: Satin weave, harness weave, fish weave and unidirectional. All of these are just different weave patterns for carbon fabric. In almost every automotive application 1×1 or 2×2 weave is superior in looks and construction which is why you rarely will hear these other weave types. Only custom or unusual carbon fiber requests will require weaves like these. Unidirectional weave is where almost every fiber is aligned in the same direction. This kind of weave is only held together by the occasional strand of either carbon or polyester running across the fibers at a 90 degree angle. This kind of carbon fiber is best used where all the force is aligned in one direction, such as in an archery bow and arrow.

Unidirectional Carbon Weave

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So which weave pattern makes for the strongest fabric?

Contrary to popular belief, the 1×1 or plain weave is actually weaker then the 2×2 or a 4 harness satin weave (4×4). This is because as the carbon fibers are put under strain or tension, the fibers want to pull straight but cannot due to the repeat of the pattern. Each fiber is forced over and under one another. Therefore, that tension will eventually shear apart the fabric, leaving a 2×2 with more tensile strength than a plain weave.

Now that you have an understanding of carbon fiber weave types, next is to discuss the major types of carbon fiber cloths. In the auto industry there are 2 popular types of cloth, wet and dry prepreg.

1. Wet Prepreg Cloth

Wet pregreg cloth is the most popular method for carbon fiber Front Lip Spoilers, Rear Diffusers and Trunks because it tends to be easier to manufacturer.  All that is needed is a precisely measured amount of resin or epoxy that is then poured over the fabric, making the fabric “wet”.

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2. Dry Prepreg Cloth

The dry prepreg cloth or otherwise known as “Dry Carbon” is very similar to wet prepreg as they both utilize resin or epoxy to adhere the fabric. However, unlike the wet version, the epoxy used for this cloth type has dry properties and is impregnated into the cloth. This step guarantees there is no excess epoxy, which gives it that “Dry” appearance. However, it makes the cloth sticker when at room temperature, which requires further steps to complete. This is why dry carbon parts and accessories tend to be more expensive when compared to wet carbon cloth. Once the aero parts are molded it requires baking for several hours at a temperature of 250 degrees fahrenheit. This is because it will not cure in room temperature.

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Why would I pay more for a Dry Carbon Aero Piece?

The answer is quite simple.  Dry carbon is able to create the same tensile strength as wet carbon fiber but it weighs substantially less.  So for all your auto enthusiast looking to track your car and shed some weight, dry carbon is a must!

If you have any further questions about carbon fiber weaves or fabric please email RW Carbon at info@rwcarbon.com

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