Composites Taxonomy — Family Index
A composite is a heterogeneous material in which a discrete reinforcement phase is bound by a continuous matrix phase, the two acting together to deliver properties neither achieves alone. Engineering composites are classified primarily by matrix chemistry (PMC / MMC / CMC / CCC), then by reinforcement geometry (continuous fiber, short fiber, particulate, whisker), then by form (UD prepreg, woven, NCF, SMC). Polymer matrix composites (PMCs) — chiefly carbon/epoxy CFRP and glass/polyester GFRP — account for roughly 90% of industry volume. This note maps the full taxonomy with real product names, properties in SI, and current applications.
1. At a glance — matrix × reinforcement matrix
| Matrix → / Reinforcement ↓ | Polymer (PMC) | Metal (MMC) | Ceramic (CMC) | Carbon (CCC) |
|---|---|---|---|---|
| Continuous fiber | CFRP, GFRP, AFRP (dominant) | B/Al, SiC/Ti, SiC/Al | SiC/SiC, C/SiC, ox/ox | C/C |
| Short / chopped fiber | SMC, BMC, LFT thermoplastics | Al-Saffil (SiC short fiber) | rare | rare |
| Particulate | filled epoxies, polymer concrete | Al-SiCₚ (Duralcan) | reaction-bonded SiC variants | n/a |
| Whisker | rare | Al-SiCw (historical) | Si₃N₄-SiCw cutting tools | n/a |
| Woven / braided | woven prepreg, 3D woven, braid | preform-based MMC | preform-based CMC | C/C preforms |
| NCF (non-crimp fabric) | wind blade, marine, auto | n/a | n/a | n/a |
| Prepreg (B-staged) | aerospace primary structure | n/a | CMC slurry prepreg | n/a |
| Sheet/bulk molding (SMC/BMC) | auto body, electrical housings | n/a | n/a | n/a |
PMC volume is dominated by glass-fiber commodity composites (boats, tanks, wind, building); carbon-fiber composites are the value leader (aerospace, satellites, race cars, hydrogen vessels). MMCs are niche (brake rotors, electronic packaging). CMCs are accelerating with hot-section turbine adoption (GE9X SiC/SiC since 2016). C/C is reserved for the highest-temperature reusable structures (rocket nozzles, F1/aircraft brakes).
2. Fiber reinforcements
2.1 Carbon fiber
The dominant high-performance reinforcement. Two precursor routes drive a wide property spread:
PAN-based carbon fiber (≥90% of market) — polyacrylonitrile precursor, oxidized then carbonized at 1000–1500°C (high-strength grades) or graphitized to ≥2500°C (high-modulus grades). Density 1.76–1.83 g/cm³.
| Grade | Maker | Filament dia | E (GPa) | σ_t (GPa) | ε_f (%) | Class |
|---|---|---|---|---|---|---|
| T300 | Toray | 7 µm | 230 | 3.53 | 1.5 | Standard modulus (SM) |
| T700S | Toray | 7 µm | 230 | 4.90 | 2.1 | SM, high-strength |
| T800S/H | Toray | 5 µm | 294 | 5.88 | 2.0 | Intermediate modulus (IM) |
| T1000G | Toray | 5 µm | 294 | 6.37 | 2.2 | IM, high-strength |
| T1100G | Toray | 5 µm | 324 | 7.00 | 2.0 | IM, latest gen |
| IM7 | Hexcel | 5.2 µm | 276 | 5.52 | 1.9 | IM (Boeing 787 benchmark) |
| IM10 | Hexcel | 4.4 µm | 310 | 6.96 | 2.0 | IM, high-strength |
| AS4 | Hexcel | 7 µm | 231 | 4.41 | 1.7 | SM (legacy aerospace) |
| HTS40 | Toho Tenax | 7 µm | 240 | 4.30 | 1.8 | SM, F1 staple |
| M55J | Toray | 5 µm | 540 | 4.02 | 0.8 | High modulus (HM) |
| M60J | Toray | 5 µm | 588 | 3.92 | 0.7 | HM, satellite struts |
Pitch-based carbon fiber — mesophase petroleum or coal-tar pitch, spun and graphitized; gives the highest moduli (and highest thermal conductivity, useful for thermal management) but lower strength and high brittleness:
| Grade | Maker | E (GPa) | σ_t (GPa) | k (W/m·K) |
|---|---|---|---|---|
| K13C2U | Mitsubishi | 900 | 3.80 | 620 |
| K13D2U | Mitsubishi | 935 | 3.70 | 800 |
| YS-95A | Nippon Graphite | 880 | 3.60 | 600 |
Use cases by class: SM (T300/AS4) — sporting goods, secondary aircraft structure, industrial; IM (IM7/T800) — aircraft primary structure (wings, fuselage); HM (M55J) — satellite booms, optical benches; UHM pitch (K13D2U) — space radiators and dimensionally stable instruments.
2.2 Glass fiber
Largest tonnage reinforcement. Density 2.5–2.6 g/cm³.
| Grade | Composition note | E (GPa) | σ_t (GPa) | T_use |
|---|---|---|---|---|
| E-glass | alumino-borosilicate, low-alkali | 72 | 3.45 | 380°C |
| E-CR (boron-free) | corrosion-resistant E | 80 | 3.45 | 380°C |
| S-glass / S-2 | high-Mg, high-strength | 85–90 | 4.59 | 815°C |
| R-glass (Owens Corning) | high-modulus | 86 | 4.40 | 800°C |
| Advantex (OC) | boron-free, E-CR class | 81 | 3.45 | 380°C |
| AR-glass | alkali-resistant (ZrO₂) | 73 | 3.24 | for cement |
E-glass dominates wind-turbine blades, marine, pipe, tanks, building/insulation. S-2 (AGY) goes into aerospace radomes, helicopter rotor blades, ballistic armor backing.
2.3 Aramid (aromatic polyamide)
Para-aramid: Kevlar (DuPont) and Twaron (Teijin). Density 1.44 g/cm³ — far below carbon. Excellent tensile strength and toughness; poor compressive strength (~20% of tensile) due to fibril kinking.
| Grade | Maker | E (GPa) | σ_t (GPa) | Notes |
|---|---|---|---|---|
| Kevlar 29 | DuPont | 70 | 2.92 | ballistic standard |
| Kevlar 49 | DuPont | 113 | 3.00 | composites/cables |
| Kevlar 119 | DuPont | 55 | 3.10 | high-elongation |
| Kevlar 129 | DuPont | 96 | 3.40 | upgraded ballistic |
| Kevlar 149 | DuPont | 143 | 2.30 | high-modulus |
| Twaron 1000 | Teijin | 80 | 3.10 | ballistic |
| Twaron 2000 | Teijin | 115 | 3.20 | composites |
Use cases: soft body armor, helmets, slash-resistant gloves, marine ropes, friction products (Kevlar pulp), composite skin in canoes/kayaks, helicopter rotor leading edges.
2.4 UHMWPE fibers
Ultra-high molecular weight polyethylene, gel-spun and drawn. Density 0.97 g/cm³ — floats on water. Highest specific strength of any fiber.
| Grade | Maker | E (GPa) | σ_t (GPa) | T_max |
|---|---|---|---|---|
| Dyneema SK75 | DSM/Avient | 109 | 3.40 | 70°C (creep) |
| Dyneema SK99 | DSM/Avient | 155 | 4.00 | 70°C |
| Dyneema SK90 | DSM/Avient | 132 | 3.80 | 70°C |
| Spectra 900 | Honeywell | 73 | 2.60 | 70°C |
| Spectra 1000 | Honeywell | 113 | 3.20 | 70°C |
| Spectra 2000 | Honeywell | 124 | 3.51 | 70°C |
Drawback: low service temperature (creep above 70°C), poor matrix adhesion (requires plasma/corona treatment). Use cases: hard ballistic armor (Dyneema HB80, HB210), high-strength ropes, sailcloth, cut-resistant gloves, fishing line.
2.5 Other fibers
- Boron fiber — CVD of B on tungsten core, 100–200 µm diameter, E ≈ 400 GPa, σ_t ≈ 3.6 GPa. Used in F-14 horizontal stabilizers and F-15 vertical stabilizer skins (1970s–80s). Largely displaced by carbon; still in some sports goods (tennis, fishing rods) and patch repair (B/Ep prepreg by Specialty Materials).
- PBO (Zylon, Toyobo) — poly-p-phenylene-2,6-benzobisoxazole. E ≈ 270 GPa, σ_t ≈ 5.8 GPa. Highest strength textile fiber. UV/hydrolysis degradation is severe — withdrawn from primary body armor after Zylon vests were found to lose strength in service (NIJ recall, 2005). Used today in mooring lines, fire suits, racing helmet liners with UV barriers.
- Basalt fiber (Kamenny Vek, Mafic) — molten basalt rock spun. Density 2.7, E ≈ 89 GPa, σ_t ≈ 4.0 GPa. Higher T-resistance (700°C) than E-glass, more sustainable. Civil engineering rebar, geotextiles.
- Natural fibers — flax, hemp, jute, kenaf. Density 1.3–1.5, E 30–80 GPa, σ_t 0.4–1.0 GPa. Bio-composites for auto interior (door panels, parcel shelves), packaging.
- Silicon carbide (SCS-6, Tyranno, Nicalon NL207, Hi-Nicalon Type S, Sylramic) — for CMCs and MMCs. See §8.
- Alumina (Nextel 312/440/610/720) — 3M oxide ceramic fibers for oxide/oxide CMCs.
3. Matrix systems
3.1 Thermoset PMC matrices
| Matrix | Cure / T_g | Service T | Key use |
|---|---|---|---|
| Epoxy DGEBA + amine | 120–180°C cure, T_g 180°C | 120°C (wet) | Aerospace, marine, sporting (the workhorse) |
| Epoxy + DDS hardener | 180°C, T_g 200°C | 150°C | Aerospace 350°F-class (8552, 977-3) |
| BMI (bismaleimide) | 175°C + 230°C post, T_g 280°C | 180°C | F-22 fuselage, supersonic skins, engine nacelles |
| Cyanate ester | 180°C, T_g 250°C | 200°C | Radomes, satellite (low ε_r, low moisture) |
| Polyimide (PMR-15, AFR-PE) | 320°C cure, T_g 340°C | 290°C | Engine bypass duct, missile structure |
| Phenolic (resole / novolac) | 150°C, T_g 200°C | 200°C | FR aircraft interiors, ablative heat shields |
| UPR (unsaturated polyester) | RT or 60°C, T_g 80–120°C | 80°C | Boats, tanks, panels (low cost) |
| Vinyl ester | RT or 80°C, T_g 100–140°C | 100°C | Chemical tanks, pipe (better than UPR for corrosion) |
| Benzoxazine | 180°C, T_g 170–230°C | 180°C | Low-cure-shrink aero (Cycom 5250-5BZ) |
Aerospace prepreg matrices by name (with their typical fiber pairing):
- Hexcel HexPly 8552 (epoxy/IM7, AS4) — 787 fuselage barrels, A350 wing.
- Hexcel HexPly M21 (toughened epoxy/IM7, T800) — A350 primary.
- Toray 3900-2 (epoxy/T800) — 787 wing.
- Cytec/Solvay CYCOM 977-2, 977-3 (epoxy/IM7).
- Solvay CYCOM 5320-1 (OOA toughened epoxy/IM7) — out-of-autoclave aero structure.
- Solvay CYCOM 5250-4 (BMI/IM7) — supersonic skins.
3.2 Thermoplastic PMC matrices
| Matrix | T_m / T_g | Service T | Key use |
|---|---|---|---|
| PEEK (Victrex 150/450) | T_m 343°C, T_g 143°C | 240°C | Aero clips/brackets, oil & gas |
| PEKK (Solvay KEPSTAN) | T_m 305–360°C | 240°C | AFP thermoplastic skins (lower T_m than PEEK) |
| PEI (SABIC Ultem) | T_g 217°C (amorphous) | 170°C | Aircraft interiors (FAR 25.853 friendly) |
| PPS (Toray Torelina, Solvay Ryton) | T_m 285°C, T_g 90°C | 200°C | Fokker/Airbus access panels, brackets |
| PA66 / PA6 (Akulon, Zytel) | T_m 260/220°C | 100°C | Auto under-hood, GF-reinforced housings |
| PP (polypropylene) | T_m 165°C, T_g −10°C | 80°C | Auto interior, GMT |
| PA12 (Vestamid) | T_m 178°C | 100°C | Type-IV H₂ tank liners |
Thermoplastic prepreg / tape products: APC-2 (AS4/PEEK, Solvay), TC1200 (AS4/PEEK, Toray), TC1225 (T700/PAEK, Toray), Cetex (PEKK/IM7, Toray).
4. Reinforcement forms
- UD prepreg — unidirectional fiber tape impregnated with B-staged resin, refrigerated (-18°C, 12-month shelf). Aerospace standard. Areal weight 100–300 gsm. Example: Hexcel HexPly 8552/IM7 UD at 196 gsm.
- Woven prepreg — fabric prepreg, weave styles: plain (balanced, harder to drape), twill 2x2 (most drapable / most-used), 5HS / 8HS satin (smoothest, best drape, used over compound curvature). Hexcel HexPly 8552/AS4 8HS.
- NCF (non-crimp fabric) — multiple UD plies (0/45/90/-45) stitched together with low-stretch polyester thread. Removes crimp penalty of woven. Saertex, Chomarat, Hexcel HiMax. Wind blades, A350 spar caps.
- 3D woven — through-thickness interlocking yarns. Albany Engineered Composites for LEAP fan blades and CFM RISE; Bally Ribbon Mills, TexTech. Delamination-resistant.
- Braided preforms — biaxial / triaxial braids for tubes, frames. A&P Technology braided airframe stiffeners. RTM-able near-net preforms.
- SMC (sheet molding compound) — chopped glass + UPR/VE on B-staged sheet, compression-molded. ~25% fiber, 1.8 g/cm³. Auto body panels, electrical enclosures.
- BMC (bulk molding compound) — putty form of SMC, injection or compression-molded. Headlamp reflectors, switchgear.
- GMT (glass mat thermoplastic) — random PP/glass mat, stamping-formed. Auto load floors.
- CSM (chopped strand mat) — random glass tissue for wet layup boats.
- Tow (roving) for filament winding / pultrusion / AFP — bare fiber on bobbin. 12K, 24K, 50K filament counts for industrial; 6K and 12K for aerospace AFP.
- OOA prepreg (out-of-autoclave) — vacuum-bag-only cure, void content <1%. Solvay CYCOM 5320-1, Hexcel HexPly M56, Toray TC275-1. Enables oven-cured large structure (e.g., Airbus A220 wing).
5. Sandwich cores
Composite sandwich panels couple thin, stiff face sheets with a thick low-density core to give very high bending stiffness per unit mass.
| Core | Density (kg/m³) | T_use | Typical use |
|---|---|---|---|
| Aluminum honeycomb (5052, 5056 alloys; Hexcel CR-III, PAMG-XR1) | 30–130 | 180°C | Aircraft floors, control surfaces |
| Aramid paper honeycomb (Hexcel HRH-10, Nomex) | 29–144 | 180°C | Aircraft fairings, radomes |
| Fiberglass-phenolic honeycomb (HRP, HRH-327) | 64–192 | 200°C | High-T aircraft engine cowls |
| Rohacell PMI foam (Evonik) | 31–300 | 180°C (IG-F), 220°C (HERO) | Aircraft secondary, radomes |
| Divinycell PVC foam (Diab H, HD grades) | 45–250 | 70–90°C | Wind blade shear webs, marine |
| Airex PET foam (3A Composites T90, T92) | 80–250 | 100°C | Wind blade core, marine — recyclable |
| Airex C70 PVC | 60–200 | 70°C | Marine sandwich |
| Balsa end-grain (3A Composites BALTEK) | 96–250 | 80°C | Wind blade root, super-yacht |
| Corecell (Gurit M / SAN foam) | 60–200 | 90°C | Marine impact zones |
Honeycomb beats foam in stiffness-to-weight but is expensive and traps moisture if face-sheet damage admits water. Balsa and PET are sustainable choices in wind energy.
6. Processing routes
- Autoclave cure — gold standard for aerospace prepreg. Typical cycle: vacuum bag + 6–7 bar gauge external pressure, 180°C dwell 2 h. Equipment cost dominant; void fractions <0.5%. Used for B787 fuselage barrels, A350 wing skins, F1 monocoques.
- Out-of-autoclave (OOA) / vacuum-bag-only (VBO) — engineered prepreg cures under vacuum alone (≤1 bar). Requires resin formulated for void evacuation (e.g., Solvay 5320-1). Oven-cured, no autoclave. Airbus A220 wing, GKN Western Approach.
- Wet layup — fabric + liquid resin laid up by hand or with roller. Marine, repair, art. Lowest tooling cost, lowest quality.
- Resin transfer molding (RTM) — dry preform in closed metal tool, resin injected under 5–20 bar. High dimensional accuracy, both surfaces tooled. Used for car wheels, fan blade platforms, aircraft fittings.
- VARTM (vacuum-assisted RTM) / SCRIMP — single-sided tool, resin pulled in by vacuum through flow medium. Wind blades (60–100 m), boats, train fronts.
- Pultrusion — continuous pull of fiber + resin through heated die. Cured profile (I-beam, rebar, ladder rail). Strongmwell, Creative Pultrusions, Exel. UPR/glass dominant; CF-pultruded spar caps (Vestas).
- Filament winding — continuous tow wound onto rotating mandrel at programmed angles. Pressure vessels (Composites Horizon), CNG/H₂ tanks, rocket motor cases (Northrop GEM-63), pipe.
- AFP (automated fiber placement) — robotic head lays multiple narrow tows (3.2–12.7 mm) onto a contoured tool. Electroimpact, Mtorres, Coriolis Composites machines. B787 fuselage, F-35 inlet duct.
- ATL (automated tape layup) — wider single tape (75–300 mm) on flat/large gentle curvature. A350 wing skins.
- Thermoplastic in-situ consolidation — TP-AFP with hot gas / laser / IR heating consolidates as it places, no autoclave post-cure. Spirit AeroSystems, Collins Aerospace fuselage demonstrators.
- Compression molding — SMC/BMC heated metal tool. High-volume automotive.
- Injection molding — short-fiber thermoplastics. Under-hood, brackets.
- Resin infusion (closed cavity, large parts) — wind blade root, super-yacht hulls.
7. MMCs (metal matrix composites)
Niche but established. Reinforcement boosts stiffness, wear resistance, and high-T strength of the base metal.
| MMC | Reinforcement | V_f | Use |
|---|---|---|---|
| Al/SiCₚ (Duralcan, MC-21) | SiC particulate | 10–30% | Brake rotors (Lotus Elise S1, Porsche, mountain bikes), bicycle frames, electronic packaging |
| Al/Al₂O₃ (Duralcan F3S series) | Al₂O₃ particulate | 10–20% | Automotive engine cradles, connecting rods |
| Al/Saffil | δ-Al₂O₃ short fiber | 12–25% | Toyota diesel piston crown ring (since 1983) |
| Mg/SiCₚ | SiC particulate | 10–20% | Aerospace housings (lightweight stiffness) |
| Ti/SiC (SCS-6 monofilament) | continuous SiC | 35–40% | F119 (F-22 engine) bling rotor demonstrators, fan blades |
| B/Al (boron fiber) | continuous B | 50% | Space Shuttle Orbiter mid-fuselage struts (legacy) |
| SiC/Al (Nicalon) | continuous SiC | 50% | Aerospace stiffened panels |
| Cu/W (W particulate) | tungsten | 60–80% | Electrical contacts, rocket throat inserts |
| Cu/diamond | diamond particle | 50–60% | Heat spreaders (thermal conductivity ~600 W/m·K) |
Processing: stir casting, squeeze casting (Saffil preform infiltration), powder metallurgy + extrusion, plasma spray + HIP (continuous fiber), diffusion bonding.
8. CMCs (ceramic matrix composites)
The story of the last decade. CMCs let turbine engines run hotter (or with less cooling air) than nickel superalloys allow, raising thermodynamic efficiency.
| CMC | Fiber | Matrix | T_max | Use |
|---|---|---|---|---|
| SiC/SiC (melt-infiltrated MI) | Hi-Nicalon Type S, Sylramic | SiC matrix (CVI + slurry + MI Si) | 1315°C | GE9X HPT shrouds (Boeing 777X, in service since 2020); CFM LEAP HPT shrouds; F414 nozzle flaps |
| SiC/SiC (CVI) | Hi-Nicalon S, Tyranno SA3 | SiC by CVI | 1200°C | Combustor liners |
| C/SiC | T800, T1000 carbon | SiC (LSI, CVI) | 1500°C (inert atm) | Re-entry leading edges, rocket nozzles, F1 brakes |
| Oxide/Oxide (Nextel 610/720 / Al₂O₃) | Nextel 610, 720 | Al₂O₃ / mullite | 1100°C (long-term, oxidizing) | Exhaust mixers, combustor liners (Pratt & Whitney) |
| C/C (carbon/carbon) | PAN or pitch carbon | pyrolytic carbon (CVI) | 2500°C (inert) | Rocket nozzle throats, RCC Shuttle leading edges, F1/aircraft brakes, missile nose tips |
Manufacturing for SiC/SiC MI (the GE process): SiC fiber preform → BN/SiC fiber coating (CVI) → SiC matrix by CVI → slurry-infiltrate with SiC particles → melt-infiltrate molten Si, which reacts with embedded C to form additional SiC, sealing residual porosity. Result: dense (<5% void), oxidation-resistant CMC airfoil/shroud.
CMC adoption milestones: F414 nozzle flaps (2010); CFM LEAP HPT shroud (2016, first commercial CMC rotating-shroud part); GE9X HPT shrouds + nozzles + combustor inner liner (2020 entry into service on 777X); GE Catalyst turboprop CMC HPT blades (in qualification).
9. Comparison table (~30 rows)
| Composite | Matrix | Fiber/reinf | ρ (g/cm³) | E₁ (GPa) | σ₁_t (MPa) | T_service (°C) | Typical use |
|---|---|---|---|---|---|---|---|
| CFRP T300/epoxy UD | epoxy | T300 SM PAN | 1.55 | 135 | 1500 | 120 | sporting, F1, secondary aero |
| CFRP T800S/3900-2 UD | epoxy | T800 IM PAN | 1.58 | 165 | 2940 | 120 (wet) | 787 wing, A350 |
| CFRP IM7/8552 UD | epoxy | IM7 IM PAN | 1.58 | 161 | 2724 | 120 (wet) | aero primary (787 fuselage) |
| CFRP AS4/PEEK (APC-2) UD | PEEK | AS4 SM PAN | 1.55 | 138 | 2070 | 240 | thermoplastic aero |
| CFRP M55J/cyanate UD | cyanate | M55J HM PAN | 1.65 | 320 | 1620 | 200 | satellite booms, telescopes |
| CFRP K13D2U/epoxy UD | epoxy | pitch UHM | 1.85 | 540 | 1500 | 120 | dimensionally stable optics |
| CFRP 5HS T300 fabric | epoxy | T300 SM | 1.55 | 70 | 800 | 120 | fairings, panels (quasi-iso) |
| GFRP E-glass/epoxy UD | epoxy | E-glass | 1.95 | 41 | 1100 | 100 | wind blade spar |
| GFRP E-glass/UPR (chop) | UPR | E-glass CSM | 1.40 | 8 | 100 | 80 | small boats, panels |
| GFRP S-2/epoxy UD | epoxy | S-2 glass | 1.98 | 52 | 1700 | 120 | radomes, ballistic backing |
| GFRP E-CR/vinyl ester | vinyl ester | E-CR woven | 1.85 | 25 | 500 | 100 | chemical tanks (corrosive) |
| AFRP Kevlar 49/epoxy UD | epoxy | Kevlar 49 | 1.38 | 75 | 1380 | 120 | pressure vessels, canoes |
| AFRP Twaron/PP (laminate) | PP | Twaron | 1.20 | 18 | 600 | 80 | soft armor backing |
| UHMWPE Dyneema HB80 | PE matrix | Dyneema SK99 | 0.97 | 95 | 1800 | 70 | hard armor plates |
| SMC (auto class) | UPR/VE | E-glass 25% chop | 1.85 | 13 | 80 | 150 (cured) | hoods, tailgates, electrical |
| BMC | UPR | E-glass 15% chop | 1.80 | 10 | 50 | 150 | headlamp reflectors |
| Filament-wound CFRP COPV | epoxy | T700 / T800 | 1.55 | 140 | 2400 | 80 | H₂/CNG/SCBA pressure vessels |
| Pultruded GFRP I-beam | UPR/VE | E-glass UD+CSM | 1.85 | 25 | 250 | 80 | civil structure, walkways |
| Carbon/Nomex sandwich | epoxy CFRP skins | Nomex 48 kg/m³ | 0.10 (sandwich) | flexural EI dominated | — | 180 | aircraft floor, fairings |
| Al-SiCₚ (20%) | Al 6061 | SiC particulate | 2.77 | 100 | 460 | 300 | brake rotors |
| Al-Saffil (20% Al₂O₃) | Al-Si | δ-Al₂O₃ short | 2.84 | 105 | 360 | 350 | diesel piston ring zone |
| Ti-SiC SCS-6 | Ti-6242 | SiC monofilament | 3.86 | 220 | 1500 | 600 | bling rotor demonstrators |
| B/Al | Al 6061 | B fiber | 2.65 | 220 | 1400 | 400 | legacy Shuttle struts |
| SiC/SiC (MI, GE9X HPT) | SiC (melt-infil) | Hi-Nicalon S | 2.70 | 230 | 350 (UTS) | 1315 | HPT shrouds, combustor |
| C/SiC (LSI) | SiC | T800 carbon | 1.95 | 65 | 200 | 1500 | re-entry leading edge, F1 brake |
| Ox/Ox Nextel 610/Al₂O₃ | alumina | Nextel 610 | 2.75 | 140 | 250 | 1100 | exhaust nozzles (PW) |
| C/C 2D | pyrolytic C | PAN carbon | 1.85 | 70 | 200 | 2500 (inert) | rocket throat, brake |
| C/C 3D (rocket throat) | pyrolytic C | pitch carbon | 1.95 | 90 | 250 | 2500 | SRB throats |
| GMT (PP/30% glass) | PP | E-glass random | 1.20 | 7 | 90 | 110 | auto load floor |
| Natural-fiber (flax/PLA) | PLA | flax UD | 1.30 | 25 | 280 | 80 | bio-composite trim |
Values are nominal room-T longitudinal properties for representative laminates / forms — consult CMH-17 (Composite Materials Handbook 17) and supplier datasheets for design allowables.
10. Selection heuristics
- Aircraft primary structure (wing/fuselage) → CFRP IM7/8552 or T800S/3900-2 UD prepreg, autoclave-cured, AFP-laid. Damage tolerance comes from toughened matrix + ply scheduling.
- Aircraft secondary structure (fairings, control surfaces) → CFRP fabric prepreg + Nomex honeycomb sandwich (OOA acceptable).
- Satellite tube / antenna boom / optical bench → high-modulus pitch or M55J carbon / cyanate ester (low moisture, low ε_r, dimensional stability). Quasi-iso layups for CTE control.
- Race-car monocoque (F1, Le Mans) → CFRP autoclave (T800/HTS40 with toughened epoxy) + Nomex honeycomb. RTM for some smaller fittings.
- Wind-turbine blade (60–100 m) → GFRP E-glass NCF skins with VARTM; carbon-pultruded UD spar caps for the longest blades; PVC/PET or balsa core in shear webs.
- Boat / yacht hull → vinyl-ester or UPR with E-glass woven roving + CSM, wet layup or VARTM. Carbon for race / super-yacht.
- Hydrogen / CNG / SCBA pressure vessel → filament-wound CFRP overwrap on Al (Type III) or HDPE/PA (Type IV) liner. T700 or T800 24K tow.
- Ballistic plate (hard armor) → UHMWPE Dyneema HB80/HB210 (NIJ Level III standalone) or hybrid ceramic-front + UHMWPE backing for Level IV.
- Helmet / soft armor → Kevlar XP / Twaron CT, UHMWPE Spectra Shield laminate.
- Turbine combustor liner / HPT shroud → SiC/SiC CMC (Hi-Nicalon S + melt-infiltrated SiC) with environmental barrier coating (EBC).
- Rocket nozzle throat → 3D C/C or C/SiC; nozzle extension cone is often filament-wound CFRP.
- High-performance brake rotor (race, aircraft) → C/C (cool/dry use); C/SiC (carbon-ceramic, road cars — Brembo CCM, SGL Carbon).
- Auto body panel (low cost, high volume) → SMC E-glass/UPR compression molding; LFT polypropylene for non-Class-A.
- Bridge deck / rebar / FRP grating → pultruded GFRP (E-CR / vinyl-ester).
11. Failure modes
Composites do not yield gradually like metals. Their failure is mode-rich and inspection-critical.
- Delamination — through-thickness separation between plies, driven by interlaminar shear/peel. Concentrated at free edges and ply drop-offs. Visible in C-scan as bright echo. BVID (barely visible impact damage) leaves a small surface dent but a large internal delamination — the certification driver for compression-after-impact (CAI) allowables.
- Matrix cracking — first damage mode in tension, especially in off-axis plies. Reduces stiffness; usually not load-limiting in itself but seeds delamination.
- Fiber rupture — final tensile failure; brittle, with characteristic broom or splitting fracture.
- Fiber kinking / micro-buckling under compression — compressive strength of UD CFRP is ~60% of tensile. Aramid is especially weak (~20%). Sensitive to fiber waviness, void content, and matrix support.
- Moisture pickup — epoxy absorbs 1–2% water in service; T_g drops ~25°C per 1% moisture (the “hot/wet” knockdown). All aerospace design allowables include conditioned wet allowables.
- Galvanic corrosion — carbon fiber is cathodic to almost every structural metal. CFRP bolted to aluminum without isolation will pit the aluminum. Glass fly-isolation plies, sealants, and Ti fasteners are standard.
- UV degradation — bare epoxy and aramid surfaces yellow and chalk; paint or gel-coat required for outdoor service.
- Voids / porosity — manufacturing defects from inadequate de-bulking, resin starvation, or trapped volatiles. Each 1% voids drops interlaminar shear ~7%. Ultrasonic A-/C-scan, thermography, or X-ray CT inspect.
- Wrinkles / out-of-plane fiber misalignment — caused by tool radii too sharp for prepreg drape, ply slippage during cure. Cause strength knockdown 10–40%.
- Lightning strike damage in CFRP — high electrical resistivity (relative to Al). Mitigated with copper or aluminum expanded foil (Astroseal, Dexmet) bonded to the outer surface.
- Environmental for CMCs — silica-volatilization in steam (combustor environment); environmental barrier coatings (EBCs — Yb₂Si₂O₇, rare-earth disilicates) are mandatory for SiC/SiC in steam-laden hot gas.
- CMC processing residuals — residual silicon in MI SiC/SiC limits upper-T to ~1410°C (Si melt point).
10a. Cost and volume context
| Material / form | $/kg (2024 est.) | Annual world volume | Notes |
|---|---|---|---|
| E-glass roving | 1.5–2.5 | ~5 Mt | Commodity; wind, building, marine |
| E-CR roving | 2.5–3.5 | growing | Corrosion-resistant infrastructure |
| S-2 glass roving | 8–15 | <10 kt | Aerospace, ballistic |
| Standard-modulus carbon fiber (T700 24K) | 18–25 | ~130 kt | Industrial CF growth driver |
| IM-grade carbon fiber (IM7, T800) | 60–110 | ~10 kt | Aerospace primary |
| HM pitch fiber (K13D2U) | 1000–3000 | <100 t | Space, niche |
| Aramid Kevlar 49 | 30–55 | ~75 kt total para-aramid | Ballistic dominates |
| UHMWPE Dyneema SK99 | 35–60 | ~25 kt | Ropes + armor |
| Aerospace epoxy prepreg | 80–250 (per kg of prepreg) | — | Includes resin + fiber + processing |
| OOA prepreg | 90–270 | — | Premium over autoclave grade |
| Rohacell IG-F 51 | 35–55 (foam) | — | Aerospace foam core |
| Nomex HRH-10 honeycomb | 60–200 | — | Aerospace honeycomb |
| Al-SiCₚ ingot (Duralcan) | 8–15 | — | MMC feedstock |
| SiC/SiC CMC HPT shroud (finished) | thousands per part | — | Manufactured by GE, Safran |
The “1500 USD per kg” rule-of-thumb gap between unprocessed carbon roving and a finished autoclave-cured aerospace part captures everything between: prepregging, AFP/ATL programming, tooling, cure, NDI, machining, and certification overhead.
11a. Design and analysis essentials
A laminate’s macroscopic behavior is built up from ply properties by classical lamination theory (CLT). The 4×4 ABBD matrix relates membrane forces and moments to mid-plane strains and curvatures:
| N | | A B | | ε° |
| M | = | B D | | κ |
- A (extensional stiffness) sums ply Q-bars times ply thickness.
- B (coupling) vanishes for symmetric layups — the universal aerospace rule.
- D (bending stiffness) depends on the stacking order, not just ply count, which is why 0/45/90/-45 sequences are chosen with care.
Common ply schedules:
- Quasi-isotropic [0/+45/90/-45]ₛ — equal in-plane stiffness in all directions; baseline for fittings and pressure vessel ends.
- Soft / Hard skin — biased toward 0° (hard, e.g., wing spar cap) or toward ±45° (soft, e.g., shear panel).
- 10/10/80 rule of thumb — at least 10% plies in each principal direction (0, 90, ±45) and no more than 80% in any one direction; suppresses matrix-driven free-edge failures.
Failure criteria used in design:
- Maximum stress / strain — simplest, decoupled per direction; conservative.
- Tsai-Wu — interactive quadratic criterion, the workhorse for ply-by-ply first-ply-failure (FPF).
- Hashin — physically separates fiber-tension/compression and matrix-tension/compression modes; preferred for progressive damage.
- Puck — distinguishes inter-fiber-failure (IFF) modes A/B/C; widely used in wind energy.
- LaRC04 / LaRC05 — refined NASA criteria capturing in-situ matrix strength enhancement.
Allowables generation per CMH-17 requires hundreds of coupons across environments (cold-dry, RT-dry, hot-wet) to compute A-basis (99% / 95% confidence) and B-basis (90% / 95%) values used in flight-critical design.
11b. NDI and inspection
- Ultrasonic C-scan — pulse-echo or through-transmission, water-coupled or rolling-probe. Detects delaminations, porosity, voids, foreign objects (FOD). Aerospace receiving and post-cure inspection standard.
- Phased-array UT — beam steering for complex geometries; used on B787 fuselage barrels in production.
- Thermography (active IR) — flash-heat and watch cooling; surface-near defects, fast.
- X-ray CT — full 3D void / fiber-orientation / wrinkle mapping; lab/quality-lab tool.
- Tap test — coin tap and listen; informal triage of bond/foam-core damage in field service.
- Acoustic emission — listens during proof-pressure of COPV tanks for fiber-break activity.
11c. Sustainability and end-of-life
- Thermoset PMCs are not melt-recyclable. Routes in industrial use: mechanical grinding into filler; pyrolysis (Carbon Conversions / ELG Carbon Fibre) to recover sized rCF tow; solvolysis (Vartega) to recover both fiber and resin monomer. rCF is sold for SMC, injection-molding compounds, and BMC.
- Thermoplastic PMCs (PEEK, PA, PP composites) are inherently re-meltable; an Airbus end-of-life initiative targets TP-AFP scrap recovery.
- Wind blade circularity: Vestas EcoLite (epoxy with cleavable bonds, 2022); Siemens Gamesa RecyclableBlade (Aliancys vinyl-ester pre-cleaved chemistry); LM Wind / Carbon Rivers pyrolysis of legacy blades.
- Bio-composites (flax/PLA, hemp/PHA) target lower embodied carbon and compostable end-of-life for non-structural automotive trim.
12. Cross-references
- materials-composites
- polymers-taxonomy
- additive-manufacturing
- aerodynamics
- steel-grades
- ceramics-taxonomy
- fracture-mechanics
- fatigue-analysis
- fem-fea
- structural-dynamics
12a. Notable applications snapshot
- Boeing 787 Dreamliner — ~50% by weight composite (CFRP IM7/8552 in fuselage barrels, T800S/3900-2 in wing). One-piece fuselage barrel section is 5.8 m diameter, AFP-laid.
- Airbus A350 XWB — 53% composite; CFRP wing skins ATL-laid, NCF-based wing spars.
- Airbus A220 (Bombardier C-Series origin) — OOA-cured CFRP wing (Solvay 5320-1).
- Boeing 777X (GE9X engine) — first commercial CMC HPT shrouds in service (2020).
- CFM LEAP-1A/1B/1C — CFRP 3D-woven fan blades (Albany Engineered + Safran), CMC HPT shrouds.
- F-35 Lightning II — ~35% composite by weight; CFRP / BMI inlet duct; significant boron-fiber repair patches in service.
- SpaceX Falcon 9 / Dragon — CFRP interstage, fairings, COPV pressure vessels (helium tanks).
- Boeing Starliner / SLS — composite payload fairings and adapters.
- F1 chassis (since McLaren MP4/1, 1981) — fully CFRP monocoque; current cars exceed 7000 individual prepreg plies per chassis.
- Vestas V236-15 MW wind turbine — 115.5 m blade with pultruded carbon spar caps + glass-NCF shells (VARTM).
- Toyota Mirai / Hyundai Nexo H₂ tank — 70 MPa Type-IV filament-wound CFRP overwrap on PA liner.
- Brembo Carbon Ceramic Material (CCM) — C/SiC brake rotors, Ferrari, Porsche, Lamborghini.
13. Citations
- ASM Handbook Volume 21: Composites, ASM International, 2001.
- CMH-17 (formerly MIL-HDBK-17), Composite Materials Handbook, Vols 1–6, SAE International, current editions.
- Mallick, P.K., Fiber-Reinforced Composites: Materials, Manufacturing, and Design, 3rd ed., CRC Press, 2007.
- Daniel, I.M. and Ishai, O., Engineering Mechanics of Composite Materials, 2nd ed., Oxford University Press, 2005.
- Jones, R.M., Mechanics of Composite Materials, 2nd ed., Taylor & Francis, 1999.
- Strong, A.B., Fundamentals of Composites Manufacturing, 2nd ed., SME, 2008.
- Campbell, F.C., Structural Composite Materials, ASM International, 2010.
- Bansal, N.P. and Lamon, J. (eds.), Ceramic Matrix Composites: Materials, Modeling and Technology, Wiley, 2014.
- Chawla, K.K., Composite Materials: Science and Engineering, 3rd ed., Springer, 2012.
- Suresh, S. et al. (eds.), Fundamentals of Metal-Matrix Composites, Butterworth-Heinemann, 1993.
- Hexcel, HexPly Prepreg Technology product datasheets (8552, M21, M56), Hexcel Corporation.
- Toray Composite Materials America, T-series PAN fiber datasheets (T300, T700S, T800S, T1000G, T1100G, M55J).
- Solvay Composite Materials, CYCOM 5320-1, 977-3, 5250-4 product datasheets.
- 3M, Nextel Ceramic Textiles Technical Notebook (610, 720, 312 fiber properties).
- Evonik, Rohacell PMI Foam product data; 3A Composites, Divinycell H/HD and Airex T90 product data.
- CompositesWorld editorial archive — https://www.compositesworld.com/ (Hexcel/Toray production milestones, GE9X CMC reporting).