Carbon /carbon composite:
As we know Properties of carbon/carbon composites depend on the type of carbon fiber used (high modulus or high-strength type), fiber volume fraction, fiber distribution, and the amount of porosity.
So we’re going to mention several properties of carbon/carbon composite:

Thermal Properties:

Carbon/carbon composites can have high thermal conductivity, especially if
mesophase pitch-based carbon fibers are used, carbon fibers have highly oriented carbon fibers with a highly oriented graphitic structure. This means that one must have proper fiber configuration to obtain the desired thermal conductivity.

Frictional Properties:

Carbon/carbon composites have good tribological properties against most surfaces, in addition to adequate strength, good toughness, and high thermal conductivity.

Ablative properties:

Space vehicles, on reentry into the atmosphere, are subjected to intense aerothermal loads (external surface pressure, skin friction, and aerodynamic heating). Intense heating occurs which lead to extremely high temperatures. We use thermal protection systems (TPS) made of suitable materials in order to keep special vehicles, occupants, and equipment safe.


Applications:

Major applications of carbon/carbon composites involve uses at high temperatures, for example, as heat shields for reentry vehicles, aircraft brakes, hot-pressing dies, and high-temperature parts such as nozzles.

Brakes for racing cars and some high-end luxury cars are the latest entry. Heat shields and nozzles aremade of multidirectionally reinforced carbon/carbon composites.
Lack of oxidation resistance is a major problem, and a great deal of effort has been put into the development of oxidation-resistant coating for carbon fibers, with SiC coating being the primary coating material.

Carbon/Carbon Composite Brakes

Brakes are one of the major applications of carbon/carbon composites. An
example of a carbon/carbon brake assembly used on a Boeing 767 plane . Brakes, aircraft or automobile, must have the following general requisites

(a) Oxidation resistance;
(b) High thermal capacity;
(c) Good strength, impact resistance, strain-to-failure;
(d) Adequate and consistent frictional characteristics;
(e) High thermal conductivity.


°Other Applications:

Among other aerospace applications of carbon/carbon composites, one may cite their use in rocket propulsion components and reentry thermal protection of a spacecraft.Among nonaerospace applications, there are examples of the use of carbon/carbon composites as implants as well as internal fixation of bone fractures because of their excellent biocompatibility.

The Formula 1 racing cars usually use a new set of brake linings for each race. Aircraft brakes, on the other hand, are required to survive 2000–4000 landings. An Airbus A380 has 16 sets of brakes; each brake costs something between US$25,000 to 45,000. However, use of carbon/carbon composite brakes results in weight savings relative to the conventional steel brakes; a saving of 215 kg on a plane such as Boeing 737. This allows more payload and/or fuel savings.

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