Carbon fiber materials, known for their high strength and light weight, are widely used in many fields, such as fishing rods, badminton rackets, bicycles, cars, and even airplanes and rockets. For example, the C919, China’s large passenger aircraft, uses carbon fiber composite blades in its engines.

But why is carbon fiber not used in tanks? Here are several points of understanding and analysis:

1. Strength-to-Weight Ratio vs. Toughness

While carbon fiber excels in strength-to-weight ratio, it is not as tough as steel and other materials, especially when impacted. Tanks are often directly subjected to impacts from shells, landmines, and explosive shocks. Although carbon fiber is strong, it is more likely to **fracture or break** under direct impact, while steel and other armor materials can better absorb and dissipate this shock energy. Steel offers superior toughness and shock resistance, especially in absorbing explosive energy. While carbon fiber has excellent tensile strength, it is more brittle, meaning it could crack under heavy impacts or blunt force.

2. Cost and Production Challenges

The production cost of carbon fiber is extremely high, especially for large-scale production. Manufacturing carbon fiber requires high temperatures and specialized processes, making it far more expensive than steel or other traditional tank materials. Using carbon fiber to manufacture an entire tank would significantly increase costs. Furthermore, carbon fiber is more **difficult to repair** compared to metals, particularly in battlefield conditions. If a tank's carbon fiber structure is damaged, it is more complex and time-consuming to repair than metal armor.

3. Ballistic Protection

Military tanks use composite armor (made from materials like ceramics and metals) primarily to provide enhanced protection against various threats, including kinetic energy penetrators and **anti-tank weapons**. Composite armor prevents penetration while remaining relatively light. Carbon fiber alone cannot provide sufficient ballistic protection to meet the needs of military tanks. To make carbon fiber viable in this field, it would need to be combined with other materials, such as ceramics or metals, to form a composite armor system that balances lightness with protective capability.

4. Thermal Stability and Environmental Adaptability

Tanks operate in extreme environments, including high and low temperatures, and carbon fiber performs poorly in these conditions. Carbon fiber’s thermal conductivity differs from that of metals, which may lead to uneven heat distribution, especially when tanks are exposed to the high temperatures generated by combat.

5. Structural Integrity Under Stress

Tanks often endure **extreme shear stresses**, torsion, and bending, especially when driving over rough terrain or encountering obstacles. Carbon fiber can be used in structures that experience lighter, more controllable forces, but it does not maintain **structural integrity** under the continuous dynamic loads typical of tank operations. This is especially true in **high-frequency fatigue conditions.

6. Vulnerability to Fire and High Temperatures

Unlike metals, carbon fiber is more vulnerable to high-temperature damage and could even ignite in certain circumstances, especially when exposed to fire or high-energy impacts. While composite materials are generally designed to have some fire resistance, under the extreme high temperatures found on the battlefield, the integrity of a carbon fiber structure could be compromised, particularly if the tank is struck by high-temperature weapons, such as incendiary bombs or explosives.

Why Can't Carbon Fiber Be Used to Build Tanks?

Although carbon fiber excels in certain applications, it is generally not suitable as the primary material for tank structures. Tank designs require materials with toughness, high-temperature resistance, and cost-effectiveness, and steel or advanced composite armor is better suited to meet these needs. Carbon fiber could be used more effectively in non-critical components, such as internal frames, secondary armor, or internal structures, where reducing weight can improve mobility and reduce fuel consumption, but it is not suitable as the main armor material for tanks.

 In short, although traditional metal materials and composite armor are still the first choice for military tanks due to their shortcomings in toughness, cost, and repair difficulty, carbon fiber materials still have broad application prospects in many fields, and are being used more and more.