There are various reasons to use carbon fiber in cars.
What is carbon fiber? First invented in 1860 by Sir Joseph Wilson Swan to use in incandescent light bulbs, it is an extremely strong and rigid type of carbon fiber reinforced plastic - or CFRP. It consists of layered carbon fiber cloth, with the fibers connected and held together by a binding matrix in the form of a thermoplastic polymer or thermoset resin. It is time-consuming and expensive to produce but the result is a stable material with a very high strength-to-weight ratio. It's more than 20% lighter than an equivalent aluminum component and half the weight of a steel component.
In order to produce a carbon fiber component, these steps must be completed:
Thanks to the material's strength and low weight, carbon fiber components such as crash structures are used in auto racing to protect the driver; examples include gymkhana, drag, rally, and circuit racing, which you can read more about here. It can be used for some body panels on all types of steel or aluminum cars - such as the doors, hood, and trunk lid to reduce weight. Creating carbon fiber car accessories and interior parts confers very few actual advantages except for bragging rights. However, these are seen as exclusive carbon fiber design elements and are often offered as an expensive option on a premium vehicle.
At the expensive end of the market where the use of carbon fiber for cars' bodies can be justified, there are quite a few examples of the full carbon fiber car, in which the entire structure and body are made of carbon fiber:
From these, two cars stand out. One is the Alfa Romeo 4C, which is the cheapest car composed almost completely of carbon fiber. The other is our favorite premium hatchback from among all the premium new luxury cars currently available - the BMW i3. It is an oddball yet advanced EV with full carbon construction that was ahead of its time when it was launched. Its carbon technology has filtered down to BMW's other new sports car models; for example, BMW uses exposed-weave carbon fiber sheets for all M cars' roof panels.
For that touch of exclusivity, carbon fiber wrap for a car is a vinyl wrap with an imitation carbon weave printed on it. Various components can be covered in this wrap to make it appear as if these parts are made from carbon fiber. Some people cover just the hood, roof, spoiler, or body kit, but the entire car can be wrapped in a carbon wrap if the owner wants a full-carbon look. The owner can wrap rims in carbon fiber, too.
As electric cars with heavy battery packs become more widely available, lightweight carbon fiber will probably play a bigger role as a car-body material. However, at the moment, it is still a very specialized job to work with carbon fiber and it's costly to produce, so its use for large and structural components remains limited to more expensive cars. Improving technical processes and breakthroughs such as Lamborghini's "forged composite" process to greatly speed up production might eventually reduce its cost and bring it into the mainstream.
For panels featuring exposed carbon fiber, around 3,000 fiber filaments are used per bundle - also called a roving - to create the distinctive weave patterns visible behind the clear lacquer topcoat. For stronger, hidden, or painted parts, these rovings can contain as many as 50,000 filaments, which does not produce a finish with the distinctive weaved appearance. In order to achieve the right appearance, a lot more of the process of creating exposed carbon fiber is done by hand, unlike structural carbon fiber, making the latter quicker and easier to produce.
Here are a few facts and figures: With a tensile modulus of around 290 million psi, the strongest carbon fiber is around ten times stronger than steel, yet not as strong as titanium. The strongest weave patterns for carbon fiber are usually plain or twill weaves.
All the different types of carbon fiber are composites and not metals. None of the ingredients used in the production of carbon fiber is metallic or derived from metals. In a composite, two materials with different properties are merged to form a new material with its own unique properties - in carbon fiber's case, the carbon fibers and the binding polymer. There are various types of carbon fibers using fiber rovings of various thicknesses and binding polymers that may be, among others, epoxy or thermoplastic polymers such as vinyl ester or polyester.
The complicated manufacturing process means that carbon fiber is still, on average, roughly ten times more expensive than steel. However, this is still a vast reduction from what it cost a few decades ago when it was still very rare and cost more than 30 times as much as steel.
The Alfa Romeo 4C is probably among the cheapest used cars one can buy with a full carbon fiber car frame and body. These can be bought used for less than $50,000 now.