Carbon Fiber Composites

Carbon Fiber Composites – Advantages and Disadvantages

Carbon fiber relates to outstanding material in many respects. However, as with every material, it features with some advantages and disadvantages also. This article describes 4 big advantages and 4 disadvantages of carbon fiber composites.



Advantages

Stiffness

Carbon fiber composites feature with outstanding stiffness to weight ratio thanks to density (and weight) almost 2 times lower comparing to aluminum and almost 5 times lower compared to steel.

Available carbon fiber features with various stiffness and fabric weave and the most widely used one feature with standard stiffness and 2/2 (twill) or 1/1 (plain) weave. Carbon fiber fabric for standard purposes offers average (medium module carbon fiber) or high stiffness (high module carbon fiber)  that is 2 times stiffer than one provided by standard carbon fiber fabrics (and more costly also).

Additionally, in case of element exposed to stress at one or two directions, where consistent strength is not required at any direction, stiffness may be increased by using singe-direction fabric that offers 90% stiffness at the given direction what results in improved stiffness of carbon fiber composite. In the case of aluminum or steel, it is not possible due to a single-direction structure that features stable stiffness and strength.

Low Weight

Carbon fiber composites feature with low density and low mass. Carbon fiber composites feature with a density of 1.6 g/ cm3 that in case of aluminum is 2.7g/cm3 and 8 g/cm3 in case of steel. Therefore a steel panel 10mm thick and sized 1x1m weighs approx. 80kg, aluminum one 27kg whereas carbon fiber panel weighs 16kg, which is 5 times lower than the steel one. And this the main reason behind a wide use of carbon fiber composites in F1 racing cars or automated machine gripping devices, where weigh is a crucial factor.



Carbon fiber composites

Attractive Appearance

Carbon fiber products are covered with a clear topcoat very often to demonstrate a unique and beautiful appearance of carbon fibers. During the manufacturing of carbon fiber products, the first top layer is made from low weight fabric (200-300g) of specific weave – that offers an attractive appearance, e.g. fabric featuring 1/1 weave is used in Ferrari cars whereas one with 4/4 weave is used in Pagani and Koenigsegg cars. Most carbon fiber products are made manually what makes every item very unique. Therefore the whole process relates to a kind of art and carbon fiber product suppliers very often place a serial number on each product or part to emphasize its unique and original style.

Short Series Production Possible

Manufacture of elements including device casing made from steel and aluminum requires significant and costly investment. In the case of plastic manufacture very costly molding injection machines are required and the implementation process, which pays off only for series production including thousands of items. Whereas the production of products made from aluminum requires forming with expensive molds and presses. And that is the reason behind the development and manufacture of carbon fiber products. This technology includes 3D drawing based milling of master-model that enables the delivery of composite molds made from resins and carbon or glass fabric. Implementation of this technology does not require investment related to plastic or aluminum and it makes the manufacture of 20-30 items possible.



Disadvantages

High Cost

Carbon fiber relates to a costly material where a square meter of carbon fabric or ready pre-preg (resin-impregnated carbon fiber) costs as much as  50 EUR. In practice, any carbon fiber composite includes a few layers (mostly from 4 up to 10 layers). Placement of any additional layer inside the mold is time-consuming manual work and the production process of high-quality carbon fibers composites (prepreg composites) requires costly equipment including autoclave what increases a unit price.

Fragile

Carbon fiber relates to a material used for the manufacture of components exposed to repeated stress and impact. Any strong impact e.g. hitting with a hammer may result in carbon fiber composite cracking. Therefore aramid has been developed and its layers placed additionally improve significantly impact resistance of carbon fiber. Interestingly aramid is not visible as it is placed inside carbon fiber composite.

Time-Consuming Manufacture

Carbon fiber manufacture is a technology that is more time-consuming comparing to molding injection. Some big international concerns (like BMW) implemented production of carbon fiber parts using automated machines and heating presses to ensure hardening of carbon composite within 5 minutes, but in case of small and medium series production, a carbon fiber part is manually handled at high precision to maintain unique appearance of carbon fiber structure and prevent any composite defects. In practice placement of carbon fabrics in case of bonnet may take as long as 2 days. Consequently, some restrictions apply during the production of high volume manufacturing.



Not Each Product Can Be Manufactured From Carbon Fiber

Carbon fiber features with some restrictions due to work method used during production, namely placement of fiber fabric inside molds. Actually, some conditions need to be met for carbon fiber products, in particular with reference to an internal structure namely dashboard components, where the structure is made from carbon fiber and some assembly parts are made from plastic and installed by bonding to carbon fiber main component.

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