There are a number of reasons why carbon composite is replacing steel. Some of them are as follows.

1. The specific strength and specific modulus (strength and modulus per density) of carbon composite is much greater than steel. For any transportation application including aerospace, it is this specific property rather than absolute property is important. By making the car lighter, the energy consumption for the same speed or passengers is lower, making the car greener and reduces the carbon dioxide production.

2. Carbon composite does not corrode while steel is easy to corrode.

3. Using steel, you need to make so many parts which must be put together by nuts and bolts. This requires unnecessary parts such as nuts and bolts, weakens the joint that has holes, and worst of all labor cost to put together many parts are costly. Carbon composite can make a one large, complex shaped product that does not need to put together.

4. When a car crashes, the fiber reinforcements pulls consuming a large amount of energy. Thus, the impact energy is not transferred to the driver or passengers, but is absorbed by the friction energy due to the interfacial slippage, saving lives.

There are many more, but these are the important reasons. However, carbon fibers are rather expensive. This is the reason why carbon fiber composite was not used for cars until recently, despite the fact that advanced aircrafts are all made by carbon fiber composites, in particular jet fighters. It is important to note that if you compare raw material alone, carbon fiber composite is much more expensive than steel. However, since it saves lots of labor costs, the system cost, considering the labor cost of putting together parts can be saved. Thus, you should avoid raw material comparison, and evaluate the system costs. Processing of carbon fiber composite is more difficult than simple stamping of steel plate. Since BMW and other high cost cars started using carbon composite parts, it will trickle down the benefits soon and in the near future, even a standard car might use carbon fiber composites. This trend will accelerates as the electric car becomes the main stream of the automotive industry.

Dear Shubham Patil,

Prof. Ishida explained most impartant thecnical advantages why the carbon fiber reinforced composites prefered instead of the steel. I want to add my view, as well. Even the carbon fiber reinforced composites used in some part of the automobile, still critical load carring parts such as the chassis, the frame, the cross rails etc. are steel. Generally, some expensive automobile models used the carbon fiber composites for the interior design. Maybe, some superexpensive or concept design automobiles could be produced by all carbon fiber reinfoced composites but not an ordinary budget ones. I think, even the steel is heavy according to the carbon fiber reinforced composites, it will continue to be used for the middle-cost and the low-cost automobiles.

Cheers,

Cemal

There are no. of reasons.

Few are;

1. have high strength to weight ratio

2. high load-bearing capacity

3. are durable

4. are stronger etc.

yes