Aluminium Sandwich Panels: Honeycomb, Corrugated, Foam and ACP Cores Compared

What is an aluminium sandwich panel?

A sandwich panel works like an I-beam spread into a sheet. The two aluminium skins act as the flanges and carry bending as tension and compression; the core acts as the web, holding the skins apart and carrying shear. Because bending stiffness grows with the square of the distance between the skins, a thick, light core multiplies stiffness at almost no weight cost.

A quick calculation shows the effect. Two 1 mm aluminium skins on an 18 mm aluminium honeycomb core give a 20 mm panel weighing about 6.5 – 7 kg/m². A solid aluminium sheet of the same weight is only about 2.5 mm thick. The sandwich panel is well over 100 times stiffer in bending, which is why it can span between widely spaced supports without visible deflection or oil-canning.

All aluminium sandwich panels share the skins’ advantages: corrosion resistance, a surface that can be coil-coated, anodised or printed, easy cutting and full recyclability of the metal. Their differences come from the core: its material, geometry and how it is bonded to the skins. Those choices determine fire performance, impact resistance, acoustic behaviour, formability and price.

The five main types of aluminium sandwich panel

Aluminium honeycomb panels in detail

Honeycomb core is made by printing adhesive lines on aluminium foil, stacking and curing the sheets into a block, slicing it and then expanding it into hexagonal cells. Cell size (commonly 3/16 – 3/4 in, or 4 – 19 mm), foil thickness and alloy set the core density, typically 30 – 130 kg/m³ for commercial and aerospace grades. Denser core gives higher crush and shear strength.

Some catalogues quote skin thicknesses of a few hundredths of a millimetre; that is foil-core gauge, not skin gauge. Facade honeycomb panels use skins of roughly 1 mm.

Honeycomb panels are the default for metro and rail car interiors, aircraft floors and galleys, ship cabins and bulkheads, cleanroom walls, elevator cars, exhibition systems and large architectural facade and soffit panels. Because the core is anisotropic (stronger in the ribbon direction), panel orientation should follow the main span. See our honeycomb sandwich panel guide and honeycomb core specification for depth on core grades.

Corrugated core panels (ACCP)

A corrugated core panel replaces the honeycomb with a continuous formed sheet, usually 0.2 – 0.5 mm aluminium, rolled into a wave or cone pattern and bonded between skins of 0.5 – 1.0 mm. The result is an all-aluminium panel with no plastic core and a much simpler manufacturing route than expanded honeycomb.

Corrugated panels are stiffest across the flutes and somewhat less stiff along them, so long spans should run across the corrugation. They bend and roll into curves more easily than honeycomb panels because the core does not crush as readily, which makes them popular for curved facades, column covers and vehicle side walls. Our sandwich wall panel guide compares corrugated and honeycomb walls for facade systems.

Aluminium foam sandwich panels (AFS)

Aluminium foam is made by injecting gas into molten aluminium or by heating a compacted powder with a foaming agent, giving a closed-cell metal sponge with a density commonly between about 0.2 and 0.8 g/cm³. Bonded between aluminium skins it forms an AFS panel that is heavier than honeycomb but isotropic, crushes progressively under impact and absorbs sound.

For deeper information on foam itself, see our foam aluminium guide.

Aluminium composite panels (ACP / ACM)

ACP is the thinnest and most widely used aluminium sandwich: two coil-coated skins, typically 0.3 – 0.5 mm, continuously laminated to a 2 – 5 mm core. Total thicknesses of 3, 4 and 6 mm are standard. It is flat, light, easy to rout and fold into cassettes, and comes in any colour, metallic, wood or stone finish.

Fire classes depend on the tested product and fixing system. Always check the classification report and local building code. Following the Grenfell Tower fire in 2017, many jurisdictions banned PE-core ACP on tall buildings.

Skin alloy for ACP is usually 3003 or 5005 (sometimes 1100 or 3105) in an H-temper, coated with PVDF for exterior use or polyester for interior and signage. Our ACP skin coil page covers the coated sheet used by panel producers.

Sandwich panel types compared

Values are typical ranges for comparison; specific products and test reports govern.

As a rule, start with ACP when the panel is small, flat and mainly decorative and the building code allows its core. Move to corrugated or honeycomb when the panel is large, must be non-combustible, or must span further between supports. Choose foam only when impact, blast or acoustic absorption justifies its weight and cost.

Finishes, colours and fabrication

Panels can be cut by saw, router or waterjet; ACP and corrugated panels are routed on the back skin and folded into trays or cassettes. Honeycomb panels need edge closure (folded skin, extruded edge profile or potting compound) and inserts where fixings carry load. Laser cutting is generally avoided on polymer-core panels. Metline can supply panels cut to size and the aluminium extrusions used as edge profiles and sub-frames.

Design and installation points for sandwich panels

Panel selection is only half the job; most problems on site come from movement, fixing and moisture. Aluminium expands by about 0.024 mm per metre for every degree Celsius, so a 4 m facade panel that sees a 60 °C swing between a winter night and a summer afternoon changes length by close to 6 mm. Fixing systems must let each panel slide on at least one edge, usually through slotted holes or hook-on cassette brackets.

Wind load decides panel thickness and support spacing. Facade engineers check bending stress in the skins, shear stress in the core and deflection, typically limited to span/100 to span/200 depending on the code and the visual requirement. For honeycomb and corrugated panels the core shear strength often governs short, heavily loaded spans, while skin stress governs long spans.

For floors and decks in vehicles and ships, the critical cases are point loads from heels, trolley wheels and equipment feet. A denser core or a thicker top skin resists local indentation better than simply increasing overall thickness. Where panels will be walked on or loaded by trolleys, ask for core crush strength and a local indentation test result, not just the panel’s overall bending data, and consider an anti-slip embossed or tread-pattern top skin.

Where aluminium sandwich panels are used

• Building facades: rainscreen and ventilated facade panels, soffits, column covers and canopies
• Interiors: ceilings, partitions, feature walls, lift cars and cleanroom walls
• Rail and metro: car side walls, ceilings, floors, doors and luggage racks
• Road vehicles: bus and coach panels, truck bodies, refrigerated boxes and caravans
• Marine: cabin walls, bulkheads, decks and furniture on ships and yachts
• Aerospace: floors, galleys, control surfaces and satellite structures (aerospace honeycomb grades)
• Signage and display: sign trays, exhibition stands and point-of-sale displays
• Industrial: machine guards, acoustic enclosures and equipment housings

Common mistakes when specifying sandwich panels

• Choosing by thickness alone. Two 4 mm panels can differ greatly in skin thickness and stiffness; specify skin alloy and gauge.
• Assuming any metal panel is non-combustible. The core and adhesive decide the class. Ask for the EN 13501-1 or ASTM E84 / NFPA 285 report for the exact build-up.
• Ignoring span direction. Honeycomb and corrugated cores are directional; orient the panel to the main span.
• Leaving edges open outdoors. Water entering honeycomb cells can freeze or corrode; seal or close edges.
• Fixing through the core without inserts. Cores have low bearing strength; use bonded inserts or edge extrusions.
• Mixing coating batches on one elevation. Order a full facade from one coil batch to avoid colour variation.

Related honeycomb, foam and panel pages

How to order aluminium sandwich panels

1. Define the panelCore type, total thickness, skin alloy and thickness, panel size, finish and colour.
2. State the performanceFire class required (and the standard), wind or floor loads, acoustic or thermal targets.
3. Confirm processingCut-to-size, routing, perforation, edge closure and inserts, or supply as flat stock.
4. Sample and approveColour and build-up samples, plus test reports for the specified product.
5. ShipPanels with protective film, packed flat in wooden crates; mill and coating certificates; EXW, FOB, CIF or DAP worldwide.

Aluminium (aluminum) sandwich panels: frequently asked questions