Composite Materials

Composites put a strong fiber inside a resin so the part gets the fiber's strength and the resin's shape. In the machinable, plate-and-tube form we stock they solve problems metals and plain plastics cannot: G10 / FR-4 glass-epoxy insulates at 500 V/mil while carrying structural load and holding ±0.1 mm; carbon-fiber laminate matches aluminum stiffness at 60 % of the weight with no thermal expansion; canvas phenolic is a self-lubricating, arc-resistant bearing material that machines like hardwood. They are anisotropic, they do not weld or form after cure, and they eat cutting tools — so they are chosen for a property, not for convenience.

Composites by reinforcement

Glass-fiber laminatesE-glass cloth + epoxy or melamine · G10, FR-4, G11, G7, G51990 – 275The universal machinable insulator: G10 / FR-4 for fixtures, standoffs, PCB stiffeners and cryogenic supports; G11 for 180 °C; G7 (silicone resin) for 220 °C and arc resistance; G5 melamine for arc and track resistance in switchgear.

Phenolic laminatesCanvas, linen or paper + phenolic resin · CE, LE, XX1580 – 95Bearings, gears, wear strips, jigs, arc chutes and terminal boards: canvas (CE) for toughness and bearings, linen (LE) for finer machined detail and small gears, paper (XX) for cheap electrical insulation.

Carbon-fiber compositesCarbon cloth or UD + epoxy · CFRP plate, tube · chopped-carbon nylon (Onyx)2337 – 600Structural plates, arms, frames, brackets and tubes where stiffness-to-weight is the whole design; Onyx and other carbon-filled nylons for printed fixtures and end-effectors with near-aluminum stiffness.

Aramid & specialty reinforcementsKevlar, basalt, hybrid weaves13—Impact, cut and ballistic resistance, abrasion liners, and hybrid layups where carbon alone is too brittle; laser-cut sheet and machined plate.

Metal- & ceramic-matrix compositesAl/SiC, Al/Al₂O₃, B/Al, SCS-6/Ti · W-Cu, Ag-W, WC-Co · ODS alloys (MA956, MA754) · CMC (SiC/SiC, Ox/Ox)25130 – 1,100Wear-resistant pistons and brake rotors, thermal-management baseplates, electrical contacts and EDM electrodes, oxide-dispersion-strengthened turbine parts; ceramic-matrix composites for hot-section and re-entry hardware. Mostly bought to shape — machining is diamond or EDM.

Sandwich core materialsPVC, PET, PMI, SAN and PU foam cores · end-grain balsa · syntactic foam · cork composite210 – 3The middle of a sandwich panel: light, shear-carrying cores bonded between skins for boat hulls, wind blades, aircraft interiors, radomes and flat structural panels; CNC-routed and thermoformed to shape.

Other compositesVarious1—Honeycomb sandwich and proprietary laminates outside the groups above.

Aluminum Composite Panel (ACM)

Choose a composite for

Electrical insulators, standoffs, terminal boards and test fixtures that must also carry load (G10 / FR-4, G11 for heat); structural plates, brackets and frames where weight and stiffness rule — drones, robotics, race cars, instruments (carbon fiber); bearings, wear strips, gears and arc chutes running dry (phenolic CE / LE); ballistic and cut-resistant panels (aramid); and cryogenic supports and thermal breaks, where G10 is the standard from –269 °C up.

Look elsewhere when

The part is loaded through the thickness or at a bolted joint without a metal insert (laminates delaminate and crush), it needs a conductive path or EMI ground (metal, or a shielded composite), it will be welded, bent or re-formed after machining, it runs above 140 °C (G10) / 180 °C (G11) / 200 °C (phenolic), or the geometry is a complex 3D solid rather than plate, tube or bar — that is a molded composite or a printed filled polymer, priced very differently. Carbon fiber against aluminum in a wet environment also drives galvanic corrosion of the aluminum.

Elastic modulus (Young's) against density, every composite grade

No materials in view have both of these properties.

Loading the library…

Composite by application

Electrical insulation under load: G10 / FR-4 for anything structural — test fixtures, busbar supports, transformer spacers; FR-4 is G10 with a flame retardant; XX paper phenolic where cost matters and loads are light.
Insulation at temperature: G11 keeps half its strength at 150 °C where G10 has gone soft; G7 silicone-glass to 220 °C with excellent arc resistance but lower mechanical strength.
Arc and track resistance: Switchgear barriers, arc chutes, contactor housings — melamine G5 and silicone G7 do not carbonize under an arc the way epoxy does.
Stiffness per gram: CFRP plate and tube for arms, frames and chassis; quasi-isotropic layup for machined plates, UD for beams; Onyx for printed brackets that would otherwise be aluminum.
Dry bearings, gears and wear strips: Canvas phenolic (CE) for bearings, rollers and wear pads; linen phenolic (LE) when the part is a small gear or needs crisp machined edges.
Impact and cut resistance: Ballistic panels, abrasion liners, protective covers and hybrid layups that stop carbon parts from shattering.
Static-dissipative fixtures: ESD-safe test fixtures, trays and handling tooling for electronics assembly — G10 strength with a controlled 10⁶–10⁹ Ω surface.

FabAgentAI

AI suggestions — verify with an engineer before ordering. Estimates are indicative; the quote page prices your exact geometry.

Manufacturing notes

CNC machining: Glass and carbon fiber are abrasive: we use diamond-coated or PCD tooling, high speed, sharp edges and full dust extraction. Tolerances of ±0.1 mm are routine on G10 and CFRP plate; phenolic machines like a dense hardwood. Edges fray and delaminate if the tool exits through the layup unsupported — we compression-route and back up drilled holes.
Design rules: Load laminates in-plane. Put a metal insert or a bushing under every bolt, keep fastener holes at least 3 diameters from an edge, avoid threads cut directly into the laminate for anything that will be re-torqued, and expect through-thickness strength to be a tenth of in-plane.
Cutting and waterjet: Waterjet cuts any laminate without heat or dust and is the economical route for flat profiles in G10, CFRP and phenolic; laser cutting works for thin aramid and G10 but chars epoxy edges. Sheet cannot be bent after cure.
3D printing: Onyx and continuous-fiber reinforced nylon print end-effectors, fixtures and brackets with near-aluminum stiffness; chopped-carbon PA12 and PETG-CF for lighter duty. Printed composites are strongest in-plane and weakest between layers, like a laminate.
Finishing: Sealed edges (epoxy or conformal coat) to stop moisture wicking into glass laminates; clear coat or paint on carbon fiber for UV protection; no plating, anodizing or welding. Phenolic and G10 accept adhesives and potting well.

Most-quoted composite grades

Grade	Reinforcement	Yield, MPa	Tensile, MPa	Density, g/cm³	Machinability	Weldability	Best for
G10	Glass-fiber laminates	240	310	1.8	Fair	Not recommended	Structural electrical insulation, fixtures
FR-4	Glass-fiber laminates	275	310	1.85	Fair	Not recommended	Flame-rated insulation, PCB stiffeners
G11	Glass-fiber laminates	260	340	1.85	Fair	Not recommended	Insulation to 180 °C
Carbon Fiber	Carbon-fiber composites	600	650	1.55	Fair	Not recommended	Stiffest, lightest structural plate
Phenolic CE	Phenolic laminates	90	75	1.37	Very good	Not recommended	Dry bearings and wear parts
Onyx	Carbon-fiber composites	37	40	1.2	Good	Not recommended	Printed stiff fixtures and brackets
G7	Glass-fiber laminates	110	170	1.8	Fair	Not recommended	Silicone-glass thermal laminate
G5	Glass-fiber laminates	90	220	1.95	Poor	Not recommended	Melamine arc-resistant laminate
Kevlar	Aramid & specialty reinforcements	280	1,350	1.38	Poor	Not recommended	Aramid impact laminate
G10-ESD	Glass-fiber laminates	240	300	1.85	Fair	Not recommended	Static-dissipative G10

Finishes for composite

All 111 finishes

14 of our 111 surface finishes take composite: 1 recommended outright, 13 with process care. Each finish opens to its datasheet — thickness, hardness, salt-spray hours, spec codes and the composite-specific notes — and the configurator prices it on the grade you pick.

Finish	Group	On composite	Thickness, µm	Hardness, HV	Salt spray, h	Cost
Electroless Copper Plating	Plating & metallizing	With care	0.2–5	80–200	—	$$$
Electroless Plating on Plastic	Plating & metallizing	With care	5–15	80–150	—	$$$$
Vacuum Metallization	Plating & metallizing	With care	0.05–1	—	—	$$$$
Primer Coating	Paint, powder & polymer coatings	Yes	15–50	—	—	$$
Conductive Coating	Paint, powder & polymer coatings	With care	15–50	—	—	$$$
EMI Shielding Coating	Paint, powder & polymer coatings	With care	15–30	—	—	$$$$
Trimming	Mechanical finishing & post-processing	With care	0	—	—	$
Nylon Part Dyeing	Marking, decoration & colour	With care	—	—	—	$
Tinted Clear Coating	Marking, decoration & colour	With care	15–50	—	—	$$

5 more finishes accept composite — see the full material × finish matrix →

Composite — frequently asked

What is the difference between G10 and FR-4?

Chemistry, none worth noting; certification, one flag. Both are woven E-glass in epoxy with the same strength, stiffness and dielectric properties. FR-4 adds a brominated flame retardant to meet UL 94 V-0, so it is the grade used for circuit boards and anything with a flammability spec. G10 is the non-flame-retardant original, preferred for cryogenic and some outgassing-sensitive uses.

Is carbon fiber stronger than aluminum?

Per kilogram, a lot: a quasi-isotropic carbon-epoxy plate has roughly the stiffness of 6061 aluminum at 60 % of the density, and unidirectional laminate is several times stiffer along the fiber. Per cubic millimeter it is comparable to aluminum in tension and much weaker through the thickness and at bolted joints. The advantage is real when the part is a plate, beam or tube loaded in-plane; it disappears on a thick machined block.

Which composite works as a bearing?

Canvas phenolic (NEMA CE): the cotton fabric holds lubricant, the resin is hard and dimensionally stable, and it runs quietly against steel at moderate speed. Linen phenolic (LE) for smaller, finer parts. G10 is too abrasive to use as a bearing surface; carbon-fiber laminate galls and wears its counterface.

How hot can G10 go?

Continuous use to about 130–140 °C; above that the epoxy softens and strength falls quickly. G11 (a higher-temperature epoxy) holds to 180 °C, G7 silicone-glass to 220 °C, glass-phenolic (G3) to about 175 °C; paper and canvas phenolics stay below about 130 °C. For higher temperatures the options are mica-glass, ceramic or a polyimide laminate.

Can you machine composites to tight tolerances?

Yes — ±0.1 mm is routine on G10 and CFRP plate, ±0.05 mm achievable on stable geometries. Two caveats: the sheet stock itself has a thickness tolerance of about ±5–10 %, so faces that need a precise thickness are machined on both sides; and glass laminates absorb moisture and grow slightly, so parts for precision assemblies should have sealed edges.