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Why is carbon fiber safer than steel for the cars?

  1. Apr 13, 2017 #1
    Not just for carbon fiber vs steel,
    I went to a seminar and heard that the team was researching how to make the steel sheets used for car making to be 'stronger', so that, a car can be safer using their material.

    Then, when I asked what does it actually mean when they say their improved steel is 'stronger' than normal steel, and their answer was higher modulus.

    As far as I know, strength, young's modulus, and toughness are different things.

    strength means it can tolerate force more before plastic deformation,
    Young's modulus or stiffness means it bends lesser for the same force,
    Toughness means more energy to deform it,

    Then, about how the skin material of a car should be to make it safer for collisions,
    Isn't it toughness that should be higher?
    more energy to deform = consume energy from the collision and lesser shock to a driver ?

    Anyhow, we can see Ferraris literally scatteringly break when an accident happens.
    Then,
    1) Why does higher strength mean more safety to the driver if it breaks anyway ?
    2) or in case when force from the collision is smaller than the capable strength?
     
  2. jcsd
  3. Apr 13, 2017 #2
    Safety in a collision is all about managing energy. Absorbing it, dissipating it, deflecting it - etc - making the steel stronger gives the designer more tools to use when designing the whole vehicle. The passenger compartment you generally do not want to be deformed in any way, all of the rest of the car you may design to absorb or deflect energy. You may still want high strength materials in these areas so you can engineer where the energy goes - for example crumple zones that crumple outward - and not towards the inhabitants.

    Also though stronger steel would allow less steel to be used for the same effective design, so reduced weight is also favorable.
     
  4. Apr 14, 2017 #3

    CWatters

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    +1 If you have a stronger material you can use less of it reducing cost. Stronger steel might allow thinner an lighter panels. Weight saving reduces fuel consumption.
     
  5. Apr 19, 2017 #4
    I think steel has more ductility but it is not a requirement for automobiles. Strength is the key factor and strength per unit weight is much more in carbonfiber that's why performance car manufacturers prefer it.

    Actually, during a collision you need a fissionable material in order to distribute the energy and momentum. If you choose too strong material the only thing that absorbes the whole energy would be you.
     
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