Fibre Reinforced Facade Encyclopedia: Materials
Carbon fibre reinforced polymer is a composite of carbon fibre in a cured thermoset resin, usually epoxy. It is spelled carbon fiber reinforced polymer in North America and abbreviated CFRP everywhere. It differs from glass fibre reinforced polymer in one property above all others: stiffness. A carbon laminate is three to eight times stiffer than a glass laminate of the same thickness at roughly the same weight, which makes it the material of choice wherever deflection rather than strength decides the section. In architectural facades that situation is uncommon, which is why CFRP is a specialist material rather than a general one.
Carbon fibre is not much stronger than glass fibre in a facade panel. It is much stiffer. If a panel is failing on deflection rather than on stress, that is the difference that matters.
At a glance
| Property | Typical value | Note |
|---|---|---|
| Fibre tensile modulus | 230 GPa standard modulus; 350 to 600 GPa high modulus | E glass is about 72 GPa |
| Laminate elastic modulus | 70 to 150 GPa typical architectural laminate | GFRP laminate is 10 to 25 GPa |
| Density | 1,500 to 1,600 kg/m3 | Slightly lighter than a glass laminate at 1,600 to 1,900 |
| Electrical behaviour | Electrically conductive, strongly cathodic | Drives galvanic corrosion of aluminium in contact |
| Fire | A polymer composite; combustible | Classified by reaction to fire test, never non-combustible |
| Relative fibre cost | Roughly 5 to 20 times E glass | The main reason it is rare on facades |
Stiffness to weight, and what it buys
Specific stiffness, that is elastic modulus divided by density, is where carbon separates from everything else used in building. A high modulus carbon laminate has a specific stiffness several times that of steel, aluminium or a glass composite. The strength numbers rise too, but for most architectural elements strength was never the problem.
The distinction matters. A thin facade panel spanning between fixings under wind load can fail two ways: the stress exceeds what the laminate can take, or the panel deflects more than the serviceability limit allows. For a fibre reinforced polymer panel the second almost always arrives first, because the laminate modulus is low relative to its strength. Raising strength does nothing for that. Raising stiffness does, and that is what carbon delivers.
Where CFRP earns its cost
- Long spanning fins, blades and louvres, where the element is fixed at one or both ends only and deflection or vibration under wind governs the section
- Deep cantilevers and unsupported projections, where a glass laminate would need a depth the architecture does not have
- Very large single panels where the fixing pattern is fixed by the design and cannot be made denser
- Kinetic and moving facade elements, where the mass being accelerated is a direct cost in the drive system
- Local reinforcement: carbon tows or strips laid into an otherwise glass laminate at the ribs, edges or fixing zones, which is by far the most common architectural use
The galvanic problem against aluminium
Carbon fibre conducts electricity and sits at the noble, cathodic end of the galvanic series, close to graphite. Aluminium sits near the active, anodic end. Put them in direct contact with an electrolyte present, which on a facade means condensation, rain in the cavity or salt laden coastal air, and you have a galvanic cell with a very large potential difference and a very large cathode area. The aluminium corrodes, and it does so quickly and locally at the contact.
This is not a theoretical risk; it is the standard failure mode when carbon composites are bolted to aluminium substructure. The controls are well established:
- Interpose an insulating barrier. A glass fibre veil or ply laminated into the carbon at every contact face, typically 0.5 mm or more, is the usual solution and can be built into the panel in the mould
- Isolate mechanical fixings with insulating bushes and washers so the bolt does not bridge the barrier
- Select fixings from a compatible metal. Titanium and austenitic stainless steel are the usual choices; galvanised and plain carbon steel are not
- Seal the joint so the electrolyte cannot sit in it, and detail the cavity so water drains away from the interface
- Where practical, avoid aluminium at the contact altogether and use a stainless or composite bracket
The same care applies to any embedded metal in the laminate and to the interface with an aluminium rail in a hook-on system.
Why CFRP is rare in architectural facades
Cost is the first reason. Carbon fibre costs several times what E glass costs per kilogram, the resins are usually epoxy rather than polyester, and the processes that get the most out of it, prepreg and oven or autoclave cure, cost far more per square metre than the hand lay-up and infusion used for glass panels. It is also black, and the weave telegraphs through thin coatings, so any other finish needs a veil and a coating system.
Then the advantage often does not apply. Facades are not weight critical in the way an aircraft or a mast is. A glass fibre reinforced polymer panel at 5 to 32 kg per square metre is already light enough that the building structure does not notice, and further weight reduction buys nothing. Where a panel is too flexible, stiffening it by geometry is usually cheaper than stiffening it by fibre.
Finally, fire. CFRP is a polymer composite with a combustible resin matrix and no non-combustibility pathway. It is assessed by reaction to fire testing exactly as any other fibre reinforced polymer is, which means on a Type A or Type B building in Australia it cannot take the Deemed-to-Satisfy route and requires a Performance Solution supported by full-scale system evidence. That is the same position as a glass composite, so carbon carries all of the fire complexity and, for most facades, none of the compensating benefit.
Standards and references
- ISO 14125 and ASTM D790 flexural properties of fibre reinforced plastics; ASTM D3039 tensile properties
- ISO 1172 and ASTM D2584 fibre and resin content by ignition loss
- ASTM G82 galvanic series data and ISO 21207 for galvanic corrosion assessment
- AS 5637.1 group number, AS 1530.3, EN 13501-1 and AS 5113 for reaction to fire of polymer composite cladding
- NCC 2022 Volume One C2D10 and Verification Method C1V3 (check the edition adopted in your jurisdiction)
Related terms
Questions specifiers ask
When is CFRP worth using on a facade?
When deflection or vibration rather than strength governs the section: long spanning fins and blades, deep cantilevers and moving elements. It is also used as local reinforcement in an otherwise glass laminate.
Why should carbon fibre not touch aluminium?
Carbon is electrically conductive and strongly cathodic, aluminium is anodic. In contact with moisture present, the aluminium corrodes rapidly at the interface. Interpose a glass fibre barrier, isolate fixings and use titanium or austenitic stainless steel fasteners.
Is CFRP non-combustible?
No. It is a polymer composite with a combustible resin matrix. It is assessed through reaction to fire tests such as AS 5637.1, AS 1530.3 or EN 13501-1, and through full-scale system testing to AS 5113 where the building type requires it.
Why is CFRP uncommon on buildings?
Cost, mainly. Facades are rarely weight critical, geometry usually provides stiffness more cheaply than carbon does, the black colour has to be covered, and carbon brings the same fire constraints as any other polymer composite.
Most architectural composite facades are glass based. ShapeShell-RT is our FRP system, with flexural strength published at 221 to 241 MPa, an AS 5637 Group 1 classification from AWTA Product Testing and a BS 8414 and AS 5113 pass at BRE Global. See ShapeShell-RT specifications
Reviewed by Richard Halvorsen, General Manager, ShapeShift Technologies. Last updated September 2026.