Standard hexagonal
The default for flat panels. Best balance of weight, flatness and strength, and the cheapest per square metre.
Honeycomb core guide
3003 Aluminium Honeycomb Core
3003 aluminium honeycomb core is a lightweight hexagonal cell structure made from 3003-H18 foil, used as the core of sandwich panels for facades, interiors, doors, transport bodies and equipment. It costs less than 5052 or 5056 core and is easier to bend and shape, with somewhat lower strength. This guide covers cell sizes, densities, typical strength, supply forms and how to specify it.
- Foil
- 3003-H18
- Cell size
- 3.2 – 25 mm
- Density
- about 20 – 130 kg/m³
- Supply
- Expanded, unexpanded, cut slices
What 3003 honeycomb core is and how it is made
A honeycomb sandwich panel works like an I-beam: two thin skins carry bending as tension and compression, and the core holds them apart and carries shear. The thicker the core, the stiffer the panel, while weight rises very little.
Aluminium honeycomb is made by the expansion process. Thin foil, in this case 3003 in the full-hard H18 temper, is printed with parallel lines of adhesive, stacked into a block and cured. The block (called HOBE, honeycomb before expansion) is sliced to the required core thickness and then pulled apart so the bonded lines become the cell walls. Each hexagon therefore has two double-thickness walls running in the ribbon (L) direction and four single walls at an angle, which is why strength and stiffness are higher in L than in the transverse (W) direction.
3003 is an aluminium-manganese alloy with good formability and corrosion resistance. Compared with 5052 foil it has lower yield strength, so for the same cell size and foil gauge the core is roughly 10 – 30 % weaker in compression and shear. In return it is cheaper, tolerates bending and pre-forming better, and is more than adequate for most architectural, interior and industrial panels where loads are moderate and the skin, not the core, sets the limit.
The parameters that define a honeycomb core
| Parameter | Typical range for 3003 core | What it controls |
|---|---|---|
| Cell size | 3.2, 4.8, 6.4, 9.5, 12.7, 19 and 25 mm (1/8 – 1 in) | Smaller cells mean more bond area, flatter skins and higher strength |
| Foil thickness | about 0.04 – 0.10 mm | Thicker foil raises density and strength |
| Density | about 20 – 130 kg/m³ (1.2 – 8 lb/ft³) | The single best predictor of compressive and shear strength |
| Core thickness (T) | about 3 mm up to several hundred mm | Panel stiffness rises roughly with the square of core thickness |
| Ribbon direction (L) | Stated on the drawing | The strong shear direction; align with the main span |
| Perforation | Perforated or plain | Perforated foil vents air during curing and in vacuum or altitude changes |
| Condition | Unexpanded block or slice, expanded sheet | Shipping volume and the work left to do on site |
Honeycomb is usually described as density – cell size – foil, for example a 5.2 lb/ft³, 1/4 in cell 3003 core. Give us those three values, the core thickness and the length and width, plus the L direction on your drawing, and the core is fully defined.
Typical mechanical properties of 3003 honeycomb
Values below are indicative typical figures for 3003 hexagonal core at about 16 mm (0.625 in) thickness, in line with published data from honeycomb producers. Compression is stabilised (with skins bonded); shear is plate shear per ASTM C273. They are not design allowables: use the test certificate for your lot or the producer datasheet for structural calculations.
| Cell size | Nominal density | Compressive strength | Plate shear, L | Plate shear, W |
|---|---|---|---|---|
| 6.4 mm (1/4 in) | 83 kg/m³ (5.2 lb/ft³) | ≈ 4.6 MPa | ≈ 2.3 – 2.4 MPa | ≈ 1.3 – 1.5 MPa |
| 9.5 mm (3/8 in) | 58 kg/m³ (3.6 lb/ft³) | ≈ 2.3 MPa | ≈ 1.5 MPa | ≈ 0.9 MPa |
| 12.7 mm (1/2 in) | 40 kg/m³ (2.5 lb/ft³) | ≈ 1.4 MPa | ≈ 1.0 MPa | ≈ 0.6 MPa |
| 19 mm (3/4 in) | 29 kg/m³ (1.8 lb/ft³) | ≈ 0.9 MPa | ≈ 0.7 MPa | ≈ 0.35 MPa |
Two patterns stand out. First, strength rises faster than density: halving density cuts compressive strength by roughly two-thirds. Second, W-direction shear is typically 55 – 65 % of L-direction shear, so the ribbon must run along the direction of highest shear load. Shear moduli follow the same pattern; for a 1/4 in, 83 kg/m³ core published L-direction shear modulus is in the region of 0.4 – 0.45 GPa.
Compression and shear tests on honeycomb follow ASTM C365 (flatwise compression) and ASTM C273 (core shear). Results depend on specimen thickness and whether the core is stabilised.
Hexagonal, over-expanded, flexible and reinforced 3003 core
Over-expanded (OX)
Cells are stretched in W into a near-rectangular shape. Easier to bend about the L axis for single-curvature panels, at some loss of L shear strength.
Flexible core
A modified cell that can follow compound curves without anticlastic bending. Used for curved facade elements and vehicle parts.
Reinforced / double-wall
Extra foil layers along the ribbon or locally around inserts raise strength where fasteners or point loads go in.
Perforated core
Tiny holes in each wall let air and moisture escape, useful for autoclave or press curing and for acoustic panels.
Thick blocks
Cores of 100 mm or more for energy absorbers, crash pads, test rigs and packaging; can be machined to shape.
3003 compared with 5052 and 5056 honeycomb
| Factor | 3003-H18 core | 5052-H39 core | 5056-H39 core |
|---|---|---|---|
| Relative strength (same cell / density) | Baseline | Higher, roughly 10 – 30 % | Highest of the three |
| Corrosion resistance | Good | Very good | Very good |
| Formability / curving | Best | Good | Fair |
| Relative cost | Lowest | Medium | Highest |
| Typical markets | Architecture, interiors, doors, enclosures, packaging | Transport, marine, industrial, some aerospace | Aerospace and high-performance structures |
Choose 5052 for marine and offshore panels, rail and bus floors, or wherever the core governs strength. 5056 is mostly specified by aerospace programmes. For most cladding, ceilings, partitions and doors, 3003 delivers the required stiffness at lower cost. A fuller discussion is in our 3003 vs 5052 honeycomb comparison.
Supply forms, sizes and tolerances
Typical supply
- Expanded sheet sizes
- 1220 × 2440 mm (48 × 96 in), 1220 × 3050 mm, 1220 × 3660 mm, 1524 × 3050 mm; other sizes cut to drawing
- Ribbon and transverse
- Expanded sheets are usually supplied slightly oversize in L and W so they can be trimmed after lamination
- Core thickness
- About 3 mm upward; thick blocks by stacking or from deep HOBE
- Thickness tolerance
- Commonly about ±0.1 – 0.15 mm on thin slices; wider on thick blocks
- Unexpanded (HOBE)
- Compact slices or blocks that expand to many times their length; cuts freight volume dramatically
- Surface
- Bare foil, or foil with corrosion-resistant pre-treatment for better adhesive bonding
Exact tolerances are agreed on the order; tell us how the core will be bonded so we can confirm a suitable thickness tolerance.
Unexpanded core is the economical choice for export because a small case of slices becomes a large volume of core. The panel maker expands it on a frame and trims it. Expanded core arrives ready to lay up but takes up far more space in a container.
Designing a panel with 3003 core
- Pick the skin firstAluminium sheet (often 0.5 – 1.5 mm 3003, 5005 or 5754 with PVDF or polyester coating), stainless steel, laminate, stone veneer or glass-fibre. Skin thickness sets surface dent resistance.
- Set core thickness for stiffnessSize the panel for deflection under wind or foot load; doubling core thickness raises stiffness roughly fourfold.
- Check core shearShear stress in the core is roughly the shear force divided by core thickness. Keep it below the W-direction value if the load direction is unknown.
- Choose cell size for skin qualityThin skins on large cells show "telegraphing" dimples. Use 6.4 mm or smaller cells under skins thinner than about 0.7 mm.
- Plan edges and insertsEdge closures, potted inserts and local reinforced core take fixings; plain core cannot hold a screw.
- Select the adhesivePolyurethane for room-temperature pressing, epoxy film or modified epoxy for hot pressing. Fire-rated facades may need a specific adhesive and test report.
A common facade example: 1.0 mm coated aluminium skins on 20 mm of 3003 core with 6.4 mm cells gives a flat, rigid panel of roughly 7 – 8 kg/m² including adhesive, far lighter than solid aluminium or stone of similar stiffness.
Where 3003 honeycomb core is used
- Building facades and ceilings: curtain-wall cladding, soffits, lift interiors and curved feature panels
- Doors and partitions: fire, clean-room, cold-store and office doors, washroom cubicles
- Transport interiors: rail and bus wall panels, truck body linings, caravan and motorhome panels
- Industrial enclosures: machine guards, worktops, clean-room walls and equipment covers
- Exhibition and retail: display stands, signage and lightweight furniture
- Air handling: airflow straighteners and vent panels in HVAC and wind tunnels
- Energy absorption: crash cushions, drop-test pads and protective packaging blocks
References and standards
- ASTM C365 – Flatwise Compressive Properties of Sandwich Cores
- ASTM C273 – Shear Properties of Sandwich Core Materials
- ASTM B209 – Aluminum and Aluminum-Alloy Sheet and Plate (foil alloy 3003)
- Hexcel – HexWeb Honeycomb Attributes and Properties (technical manual)
- The Aluminum Association – International Alloy Designations and Chemical Composition Limits
3003 aluminium honeycomb core: questions buyers ask
What is the difference between 3003 and 5052 honeycomb core?
5052 foil is stronger and slightly more corrosion resistant, so 5052 core gives higher compressive and shear strength for the same cell and density. 3003 is cheaper and bends more easily, and is standard for architectural and interior panels.
Which cell size should I use?
6.4 mm (1/4 in) is the most common for facade and interior panels. Use smaller cells under very thin skins to avoid dimpling, and larger 9.5 – 19 mm cells where weight and cost matter more than skin flatness.
What does the ribbon (L) direction mean?
It is the direction of the bonded double walls. Shear strength and stiffness are highest in L, so align it with the panel span or the main load path.
Should I buy expanded or unexpanded core?
Unexpanded core ships in a fraction of the volume and suits panel makers with an expansion frame. Expanded core is ready to bond and suits smaller users or prototypes.
Can 3003 honeycomb be curved?
Yes. Standard hex core bends in one direction with care; over-expanded core curves more easily about one axis, and flexible core follows compound curves.
Is aluminium honeycomb fire resistant?
The aluminium core is non-combustible, but the panel rating depends on skins and adhesive. Facade panels must be tested as a complete system to the local fire standard.
Can you supply cores cut to size?
Yes. Slices can be cut to thickness and expanded sheets trimmed to length and width; thick blocks can be machined to shape on request.
Need 3003 honeycomb core?
Send the cell size, density, core thickness, sheet size and supply form. We will reply with a specification check and delivered price.
