CFRP (Carbon Fiber Reinforced Polymer)
CFRP (Carbon Fiber Reinforced Polymer) is a composite used in aerospace applications. Tensile strength: 1,500 MPa.
CFRP is a material that is far lighter than metal yet just as stiff and strong — which is exactly why it has become one of the defining materials of modern rockets and spacecraft. On a launch vehicle, every kilogram you do not spend on structure is a kilogram you can spend on cargo.
Quick facts
- What it is: a composite of thousands of thin carbon fibers locked inside a hardened polymer (plastic) resin, usually epoxy.
- Density: roughly 1.6 g/cm³, versus about 2.7 for aluminum and about 4.4 for titanium.
- Weight savings: around 40% (or more) lighter than metal at equal stiffness; one university rocket module saved more than 40% versus metal.
- Strength: the carbon fibers themselves can reach roughly 1,000–3,000+ MPa in tensile strength (resistance to being pulled apart).
- Stiffness: the composite’s Young’s modulus (a measure of stiffness) can reach about 120–200+ GPa, versus about 70 GPa for aluminum.
- Specific stiffness (stiffness for its weight): can be 3–5 times that of aluminum.
- Common uses: fairings, interstages, motor cases, payload adapters, pressure tanks, and high-pressure gas bottles.
What it is and how it works
CFRP works through a simple division of labor. The carbon fibers — each only a few microns wide, thinner than a human hair — are extremely strong and stiff, and they carry the load. The polymer matrix (the surrounding plastic resin) binds the fibers together, holds them in alignment, protects them, and passes stress from one fiber to the next. Neither part is impressive alone; together they make something remarkable.
Think of it like reinforced concrete turned inside out and made featherweight: the fibers are the rebar that bears the strain, and the resin is the concrete that locks everything in place. Engineers stack many thin layers, called “plies,” and aim each layer’s fibers in the direction that layer needs to resist force. Then they cure the resin under heat (sometimes inside a pressurized oven called an autoclave) so it hardens into a solid part.
Because carbon fibers are strongest along their length, parts are engineered with the right fibers pointed the right way: a tube wound in a helix to hold pressure, a panel cross-layered for all-around stiffness. This direction-dependent behavior is called being anisotropic — the material’s strength depends on which way the fibers run, so the layup is tailored ply by ply to the expected loads.
For tanks and gas bottles, CFRP is often used as a Composite Overwrapped Pressure Vessel (COPV): resin-soaked carbon (or Kevlar) fiber is robotically wound over a thin metal or polymer liner. The liner only seals against leaks, while the composite overwrap carries nearly all the pressure load.
Why it matters
On a rocket, structural mass steals directly from payload mass, so CFRP’s mix of high strength, high stiffness, and low weight is transformational. It lets builders make larger fairings, lighter motor cases, and lighter tanks, with every kilogram saved freeing capacity for orbit. It also resists fatigue, does not corrode, and can be molded into large, aerodynamically clean, single-piece shapes with far fewer parts and joints than riveted metal. It even performs well in extreme cold: engineers have demonstrated a linerless CFRP tank holding liquid hydrogen at -253°C.
The trade-offs are real. CFRP is expensive, slow and labor-intensive to lay up and cure, hard to inspect, and brittle under sharp impact — it can quietly hide internal damage or split apart between layers (delaminate). Pressure vessels in particular have caused dangerous failures. On SpaceX’s Falcon 9, oxygen that froze in a gap between a helium COPV’s aluminum liner and its carbon-fiber overwrap was blamed for the AMOS-6 pad explosion in 2016. A separate Falcon 9 loss, the CRS-7 mission in 2015, was traced to a failed metal strut that held a helium COPV in place — the bottle broke loose and over-pressurized the tank. More recently, a COPV that failed below its expected pressure was tied to the loss of a Starship prototype during ground testing in 2025.
Where it is used: notable examples
- Ariane 6 (ESA/ArianeGroup): a carbon-fiber composite payload fairing built by Beyond Gravity, large CFRP interface structures among the largest in Europe, and an ultralight carbon-fiber Astris kick-stage structure.
- ULA Vulcan Centaur: out-of-autoclave composite structures, including heat shields with carbon-fiber face sheets over aluminum honeycomb cores.
- COPVs across the industry: carbon/Kevlar-overwrapped high-pressure helium and gas bottles, such as the helium COPVs inside Falcon 9’s propellant tanks.
- ESA / MT Aerospace Phoebus demonstrator: linerless CFRP tanks proven leak-tight with liquid hydrogen and liquid oxygen (with larger 3.5-meter tanks now in testing) — a design that could lighten an Ariane 6 upper stage by about 2 tonnes.
- International Space Station: CFRP used to replace metal parts (such as the European Standard Payload Rack) for more stiffness and strength at lower mass.
Carbon fibers (T700/T800/T1100) in epoxy matrix, 55-65% fiber volume
| DENSITY | 2 kg/m³ |
| TENSILE STRENGTH | 1,500 MPa |
| STRENGTH-TO-WEIGHT | 967741.9 kN·m/kg |
| MAX SERVICE TEMPERATURE | 177 °C |
| THERMAL CONDUCTIVITY | 5.0 W/m·K |
| THERMAL EXPANSION | 0.8 µm/m·K |
| CATEGORY | Composite |
| DESIGNATIONS | Toray T700, Hexcel IM7, Mitsubishi Pyrofil |
| MANUFACTURER | Toray / Hexcel / Mitsubishi Chemical |
| DENSITY | 2 kg/m³ |
| TENSILE STRENGTH | 1,500 MPa |
| MAX SERVICE TEMP | 177 °C |
| THERMAL CONDUCTIVITY | 5.0 W/m·K |
| THERMAL EXPANSION | 0.8 µm/m·K |
| CORROSION RESISTANCE | Excellent |
| WELDABILITY | N/A |
| MACHINABILITY | Specialized |
| COST RATING | Very High |
