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How Strong Is Carbon Fiber?

With practical applications in virtually every field you can imagine, carbon fiber material is one of the most versatile synthetic materials used in the world today—and carbon fiber strength is one of the key reasons why. It’s strong enough for bicycle and motorcycle helmets. It’s strong enough to drive a golf ball 300+ yards on the PGA Tour. And it’s even strong enough to be the reinforcing composite material on a Boeing 787. So just how strong is carbon fiber? Let us explain:

Why is Carbon Fiber So Strong?

Carbon fiber is made from crystalline carbon filaments roughly 100 times smaller than a human hair (approximately 0.0002-0.0004 inches in diameter). The carbon atoms form together in a tight, chain-like bond. The crystal alignment allows the fiber to be exceptionally strong all on its own. When combined together with other carbon fibers, the material becomes even stronger. This material can be woven into strong material or formed into permanent shapes. For being extraordinarily light in weight, carbon fiber boasts an extremely high stiffness and tensile strength. In addition to its natural strength and stiffness, carbon fiber is extremely resistant to heat and chemical abrasion making it a highly desirable material for various industrial uses.

Carbon Fiber vs Metal

To measure a material’s stiffness or resistance to deformation, we use what is called a “modulus of elasticity”. For reference, easily pliable materials like polystyrene foam or rubber have modulus of elasticities of less than 1 GPa (gigapascals) whereas concrete has measure of right around 30 GPa. Both steel and carbon fiber measure upwards of 200 GPa (Zoltek PX35 is 242 GPa for the record) which, at first glance might suggest they are roughly equal to one another in terms of strength.

Notably absent from these figures is the fact that steel is simply much MUCH heavier than carbon fiber. A unit of steel weighs about five times as much as the same unit of carbon fiber yet boasts a similar modulus of elasticity and a much lower tensile strength. Thus, when the arithmetic dust has settled, we can say that in general, and when considering strength-to-weight ratios, most carbon fibers are roughly five times stronger than steel and twice as stiff! The highest grade carbon fibers (“ultrahigh modulus”) exceed the strength of steel by a factor of ten!

Carbon Fiber Strength

Because carbon fiber carries a comparable stiffness and resistance to deformation as steel at a fraction of the weight, it is a preferred material when a product needs to be strong and lightweight. For example, carbon fiber has replaced metal alloys in many aerospace applications allowing for lighter weight and more fuel efficient planes. Carbon fiber has become a favorite material for bicycle and motorcycle helmets as well offering steel-like protection in a lightweight package. A popular material for tennis rackets and golf clubs, carbon fiber also allows athletes to boost their skills by swinging harder and faster without the risk of damaging their equipment.


Of course we’ve only begun to scratch the surface in terms of the mechanics behind carbon fiber strength. Carbon fiber is a unique and versatile material with a remarkable strength-to-weight ratio and it’s everyday applications are virtually limitless. At Zoltek, we aim to stay on the cutting edge of carbon fiber technologies and advancements. To learn more about carbon fiber strength and how its unique properties are changing the technological landscape across a wide variety of industries, visit Zoltek.com.