Material
Carbon Fiber Composite CFRP
Stiffer and lighter than any metal on a specific basis, and the only structural material whose properties you design rather than select. The cost is that the part, the material and the process are created simultaneously, so nothing about it is a commodity purchase.
Overview
Carbon fiber reinforced polymer displaced aluminum from most new airframe primary structure because it is stiffer and lighter per unit weight and does not fatigue the way aluminum does. What makes it genuinely different from every metal in this atlas is that the material does not exist until the part is made: fiber orientation, ply count, resin fraction and cure cycle are all design variables, so buying CFRP means buying a qualified process rather than a certified heat. That is why prepreg carries out-time limits and freezer logistics, why autoclave capacity is a hard constraint rather than a queue, and why substituting a nominally equivalent material system requires requalification.
Supply chain
What feeds what. Click any box with suppliers on file.
Buy a product
Forms you purchase by the pound or the piece. Each page separates mills from distributors.
Buy a service
Processes performed on material you already own.
Defense applications
Airframe primary structure
Wing skins, fuselage barrels, empennage and control surfaces where stiffness per unit weight decides the design. Carbon is also galvanically noble, which is why titanium rather than aluminum is used at composite joints.
Fuselage sections, Wing skins and spars, Empennage, Control surfaces, Access doors
Low observable structure
Radar cross section is shaped as much by material as by geometry, and carbon composite structure allows the electromagnetic behavior of a skin to be tailored in ways a metal skin cannot. This is one of the few areas where the material choice is driven by something other than mechanics.
Signature-managed skins, Inlet ducts, Edge treatments, Radome substructure
Rocket motor cases and pressure vessels
Filament wound carbon over a metallic or polymer liner gives the highest achievable pressure vessel performance factor, which directly buys range or payload.
Solid rocket motor cases, Composite overwrapped pressure vessels, Interstage structure, Payload fairings
Engine cold section
Composite fan blades and containment cases move weight out of the fan module. Three-dimensionally woven preforms are used here specifically because a two-dimensional laminate delaminates under bird strike loading.
Fan blades, Fan containment cases, Nacelle and inlet structure, Bypass ducts
Ground vehicle and naval structure
Hull structure, superstructure and shelters where weight reduction buys transportability, and where the non-magnetic behavior matters for mine countermeasures.
Vehicle hulls and armor backing, Naval superstructure, Masts and radomes, Deployable shelters
Alloys and grades
| Designation | Grade | Class | Notes | Typical forms |
|---|---|---|---|---|
| AS4 | Standard modulus | PAN-based standard modulus carbon fiber | A long-established standard modulus fiber and one of the most widely qualified in US aerospace structure. | Fiber and Tow, Dry Fabric, Prepreg |
| IM7 | Intermediate modulus | PAN-based intermediate modulus carbon fiber | The intermediate modulus workhorse of US defense aerospace, qualified across a very large number of military structural applications. | Fiber and Tow, Prepreg, Preform |
| T300 | Standard modulus | PAN-based standard modulus carbon fiber | One of the oldest qualified aerospace carbon fibers and still specified on legacy programs where requalification is not worth the cost. | Fiber and Tow, Dry Fabric, Prepreg |
| T700 | Standard modulus, high strength | PAN-based standard modulus carbon fiber | Higher strength than T300 at similar modulus, widely used in pressure vessels and filament wound structure. | Fiber and Tow, Prepreg |
| T800 | Intermediate modulus | PAN-based intermediate modulus carbon fiber | Intermediate modulus fiber widely qualified on commercial and military primary structure. | Fiber and Tow, Prepreg, Preform |
| M55J | High modulus | PAN-based high modulus carbon fiber | Very high stiffness at low strain to failure, used where dimensional stability rather than strength governs. | Fiber and Tow, Prepreg |
| 350F Cure Epoxy | Matrix resin system, thermoset | The autoclave workhorse. Toughened 350 degree F cure epoxies carry the majority of qualified aerospace primary structure. | Prepreg, Resin Systems and Adhesives | |
| 250F Cure Epoxy | Matrix resin system, thermoset | Lower temperature cure trading service temperature for cheaper tooling and lower energy processing. The general aviation standard. | Prepreg, Resin Systems and Adhesives | |
| Out-of-Autoclave Epoxy | Matrix resin system, thermoset | Formulated to reach autoclave-quality void content under vacuum pressure alone, removing the autoclave from the critical path. | Prepreg | |
| Bismaleimide (BMI) | Matrix resin system, thermoset | Higher service temperature than epoxy, into the 300 to 450 degree F range, at the cost of tougher processing and more brittle behavior. | Prepreg, Resin Systems and Adhesives | |
| Cyanate Ester | Matrix resin system, thermoset | Low dielectric constant and loss, very low moisture absorption and low outgassing, with good microcracking resistance. The space and radome matrix. | Prepreg, Resin Systems and Adhesives | |
| Phenolic | Matrix resin system, thermoset | Chosen for fire, smoke and toxicity performance and for char-forming ablative behavior rather than for mechanical properties. | Prepreg, Resin Systems and Adhesives, Honeycomb Core | |
| Polyimide | Matrix resin system, thermoset | The highest temperature polymer matrix in routine use, reaching into the 550 to 600 degree F range. Difficult to process and expensive. | Prepreg | |
| PEEK | Matrix resin system, thermoplastic | Semi-crystalline thermoplastic with excellent chemical and solvent resistance. No out-time limit and weldable rather than bonded, at high processing temperature. | Prepreg, Laminate and Panel | |
| LM-PAEK | Matrix resin system, thermoplastic | Low melt polyaryletherketone, processing substantially cooler than PEEK while keeping most of its performance. The focus of current thermoplastic aerostructure qualification. | Prepreg, Laminate and Panel | |
| IM8 | Intermediate modulus | PAN-based intermediate modulus carbon fiber | Higher performance intermediate modulus fiber, supplied in 12K filament count. | Fiber and Tow, Prepreg |
| IM10 | Intermediate modulus | PAN-based intermediate modulus carbon fiber | The highest strength intermediate modulus grade in the HexTow range. | Fiber and Tow, Prepreg |
| HM63 | High modulus | PAN-based high modulus carbon fiber | High strength high modulus fiber in 12K filament count, bridging between intermediate and classic high modulus grades. | Fiber and Tow, Prepreg |
| T1100 | Intermediate modulus | PAN-based intermediate modulus carbon fiber | Improved tensile strength and modulus over legacy intermediate modulus fibers, marketed as a new IM-plus class. | Fiber and Tow, Prepreg |
| Carbonized Rayon (C2 / NARC) | Ablative | Rayon-based carbon fiber | A rayon rather than PAN precursor fiber, used almost entirely as ablative reinforcement in rocket nozzles and heat shields rather than as structure. | Dry Fabric, Prepreg |
Properties
| Property | Value | Unit | Note |
|---|---|---|---|
| Density, cured laminate | 1.55 to 1.60 | g/cm3 | 0.056 lb/in3; roughly 60 percent of aluminum and a third of steel |
| Tensile modulus, standard modulus fiber | 230 | GPa | Fiber only; laminate modulus depends entirely on layup |
| Tensile modulus, intermediate modulus fiber | 290 to 300 | GPa | IM7 and T800 class |
| Tensile modulus, high modulus fiber | 540 or higher | GPa | M55J class; stiffness bought at the cost of strain to failure |
| Laminate modulus, quasi-isotropic | approximately 50 to 70 | GPa | A quasi-isotropic layup throws away most of the fiber's directional advantage |
| Fiber volume fraction, autoclave cured | 55 to 60 | percent | The single number that most determines laminate properties |
| Maximum service temperature, epoxy matrix | approximately 120 to 180 | degrees C | Matrix limited, not fiber limited. BMI and polyimide matrices go higher |
| Coefficient of thermal expansion, fiber direction | approximately -0.5 to 0 | micrometre/m-K | Slightly negative along the fiber, which allows athermal structures to be designed |
| Galvanic behavior | Noble | Drives aluminum corrosion at joints; titanium or isolation is required | |
| Void content, acceptable | below 2 | percent | The primary quality metric for a cured laminate, and what autoclave pressure exists to control |
Advantages
- Highest specific stiffness and specific strength of any structural material in production use
- Properties are directional and designable, so material can be placed only where load requires it
- Excellent fatigue behavior compared with aluminum
- Near-zero or slightly negative thermal expansion along the fiber, enabling dimensionally stable structure
- Does not corrode, though the metals it touches will
- Large integrated structures replace many fastened metal parts, removing joints and weight
Limitations
- The material and the part are created at the same time, so process qualification rather than material certification governs
- Prepreg has finite out-time and requires freezer storage and cold chain logistics
- Autoclave capacity is a hard physical constraint and vessels are few, large and heavily scheduled
- Poor through-thickness properties; laminates delaminate under out-of-plane and impact loading
- Barely visible impact damage can substantially reduce compression strength without visible evidence
- Galvanically noble, so it corrodes aluminum at joints and requires titanium or isolation
- Machining is abrasive rather than chip-forming, with delamination at hole exits as the governing defect
- Difficult and expensive to inspect and repair compared with metals
- Carbon fiber and PAN precursor are export controlled, which constrains who can hold the material
Governing specifications
| Designation | Body | Scope |
|---|---|---|
| NCAMP | National Center for Advanced Materials Performance | Shared qualification of composite material systems, so a material can be qualified once rather than by every program separately |
| CMH-17 | Composite Materials Handbook | The composites analogue of MMPDS: design allowables, test methods and material property data |
| AMS 3894 | SAE International | Carbon fiber tape and sheet, epoxy resin impregnated |
| AMS 2980 | SAE International | Carbon fiber fabric, epoxy resin impregnated |
| ASTM D3039 | ASTM International | Tensile properties of polymer matrix composite materials |
| ASTM D7136 | ASTM International | Damage resistance of a fiber-reinforced polymer to a drop-weight impact event |
| BAC 5317 and equivalents | Airframer process specifications | Layup and cure process control. These are proprietary and program-specific, which is why composite qualification does not transfer between primes |