Adhesive-bonded core
Light, economical and available in the widest choice of cells and densities. Limit set by the node adhesive, typically 177 °C; strength falls progressively as temperature rises towards that limit.
Sandwich core guide
High-Temperature Honeycomb Core
There is no single "high-temperature honeycomb": the usable temperature of a honeycomb core depends on the cell-wall material and, just as much, on how the cells are joined. Adhesive-bonded aluminium core is normally rated to about 177 °C (350 °F), brazed all-aluminium core removes the adhesive limit, and above the range of aluminium designers move to stainless or nickel-alloy cores. This guide sets out the temperature tiers, what limits each one and how to specify aluminium core for hot service.
- Bonded aluminium core
- Typically rated to 177 °C (350 °F)
- Brazed aluminium core
- No adhesive; alloy-limited
- Aramid core
- Typically to about 177 °C
- Limit set by
- Wall material + joining + facing adhesive
Honeycomb core temperature tiers at a glance
When a buyer asks for "high-temperature honeycomb", the first question is: how hot, for how long, and under what load? A core that survives a short paint-bake at 180 °C may be unsuitable for continuous service at 150 °C under shear load. The table groups common core families by the temperature band in which they are normally used.
| Core family | Joining method | Typical continuous service band | What sets the limit |
|---|---|---|---|
| Aramid (meta-aramid paper) with phenolic resin | Adhesive nodes, resin dip | About −55 to 177 °C | Resin system and paper |
| Glass-fibre / polyimide honeycomb | Polyimide resin | Up to about 260 °C (500 °F) extended service | Polyimide resin |
| Aluminium core, standard node adhesive | Adhesive nodes | Up to about 177 °C (350 °F) | Node adhesive, then alloy softening |
| Aluminium core, high-temperature node adhesive | Adhesive nodes | Somewhat above 177 °C; confirm with datasheet | Node adhesive |
| Brazed all-aluminium core and panels | Al-Si braze, no organic adhesive | Above bonded core; set by alloy strength retention | Softening of the aluminium alloy |
| Stainless steel and nickel-alloy cores | Resistance welding, brazing | Several hundred °C and above | Oxidation and creep of the alloy |
Bands are typical of published producer data and specifications such as AMS 4178 (5052 flexible core, 350 °F). The rating of a finished panel also depends on the facing adhesive and facing material.
Metline supplies aluminium honeycomb in this range: adhesive-bonded 3003, 5052 and 5056 core and brazed aluminium honeycomb panels. Aramid, glass-polyimide, stainless and nickel-alloy cores appear in this guide only as comparisons, so you can see where aluminium stops being the right answer.
Why the joining method decides the temperature limit
Expanded aluminium honeycomb is made by printing lines of adhesive on foil, stacking and curing the block, then pulling it open. The cured adhesive lines become the double-thickness nodes, and every bit of shear that passes through the core passes through those bonds. When the adhesive softens, node strength drops even though the foil itself is still strong.
Most aerospace and industrial node adhesives are epoxy or modified-epoxy systems qualified for service to 177 °C (350 °F). That is why the standard ceiling quoted for bonded aluminium core is 350 °F and why AMS 4178, for example, covers 5052 flexible core for 350 °F service. Producers offer node adhesives for higher temperatures, but the rating must be taken from the datasheet of that exact core product.
Brazed core and panels
Foil and facings coated with an Al-Si braze alloy are joined in a vacuum or controlled-atmosphere furnace at around 600 °C. With no organic adhesive, the panel does not outgas, will not delaminate from adhesive softening and tolerates higher temperatures, limited by the alloy.
Welded or laser-joined cells
Used mostly for metal cores and some special aluminium parts; gives an all-metal path for heat and electrical current.
The facings matter too. A honeycomb panel bonded with a 120 °C-cure epoxy film will be limited by that film, not by a 177 °C core. Always rate the complete construction: core, node bond, facing adhesive and facing material.
How aluminium honeycomb behaves as temperature rises
Aluminium foils for honeycomb are non-heat-treatable alloys (3003, 5052, 5056) in hard tempers. Their strength comes from cold work, which slowly recovers with time at temperature, and like all aluminium alloys they get weaker as they get hotter. Published producer data for 5052 core show that at 177 °C (350 °F) it keeps roughly two-thirds of its room-temperature compressive and shear strength, which is the figure most designers start from.
| Temperature band | Bonded aluminium core | Brazed aluminium core | Design comment |
|---|---|---|---|
| Cryogenic to 80 °C | Full properties; aluminium gains strength when cold | Full properties | Spacecraft and cryogenic panels use aluminium core routinely |
| 80 – 120 °C | Small reduction; check facing adhesive | Negligible change | Typical engine-bay, electronics and hot-climate exterior service |
| 120 – 177 °C | Progressive loss towards about two-thirds of room-temperature strength | Moderate reduction | Design to elevated-temperature allowables; check creep under sustained load |
| Above 177 °C | Outside standard rating unless a high-temperature node adhesive is specified | Usable, with strength falling as alloy softens | Get test data for the exact construction and exposure time |
| Above about 300 °C | Not suitable | Rarely suitable for load-bearing use | Consider stainless or nickel-alloy cores |
Older marketing figures sometimes quote 300 °C for bonded and 550 °C for brazed aluminium honeycomb. Treat such numbers with caution. Aluminium-silicon braze alloys begin to melt at about 577 °C, and hard-temper aluminium foil anneals and loses much of its strength well below that, so a brazed aluminium panel at 550 °C has little structural capacity left. Brief, low-load exposure is a different case from continuous structural service, and the specification should say which applies.
When aluminium is not enough: other core materials compared
| Property | Aluminium core (5052) | Aramid paper core | Stainless steel core | Nickel-alloy core |
|---|---|---|---|---|
| Typical maximum service | About 177 °C bonded | About 177 °C | Several hundred °C | Highest; used near combustion zones |
| Density range | Low to high (about 26 – 190 kg/m³) | Low to medium | High | High |
| Thermal conductivity | High | Low (insulating) | Moderate | Low to moderate |
| Electrical behaviour | Conductive, EMI shielding | Dielectric | Conductive | Conductive |
| Behaviour in fire | Non-combustible metal; melts near 600 – 650 °C | Chars; self-extinguishing grades | Retains shape far higher | Retains shape far higher |
| Relative cost | Low to medium | Medium to high | High | Very high |
In practice aluminium covers most sandwich panels that run warm rather than hot: engine-bay closures and nacelle areas away from the core flow, electronics and radar enclosures, hot-climate building facades, oven and dryer doors with an insulating layer, and satellite panels that cycle between deep cold and direct sunlight. Exhaust, turbine-seal and combustor zones belong to stainless or nickel-alloy honeycomb, which Metline does not supply. For a direct comparison with the main non-metallic option, read aluminium vs aramid honeycomb core.
A useful rule of thumb when screening: if the panel runs below about 120 °C, any standard aluminium core will do and the choice is about strength and cost; between 120 and 177 °C, use elevated-temperature allowables and check every adhesive in the build-up; above 177 °C, either specify a high-temperature node adhesive with test data, move to brazed aluminium construction, or add insulation so the aluminium stays in its comfortable range.
Designing aluminium honeycomb panels for heat
- Rate the whole build-up: core node adhesive, facing adhesive and facing alloy each have their own limit; the lowest one governs.
- Use hot allowables: take compression and shear values at the service temperature, then apply your usual knock-down for long-term exposure.
- Vent the core: trapped air expands when heated and can blow facings off. Perforated core or vent paths prevent pressure build-up, which also matters for vacuum and space use.
- Watch expansion mismatch: aluminium core under CFRP facings sees different expansion; it also needs a glass-ply or film barrier to prevent galvanic corrosion.
- Consider brazed construction: where outgassing, adhesive creep or long hot exposure is a concern, brazed all-aluminium panels avoid organic adhesives entirely.
- Insulate where needed: a ceramic-fibre or aerogel blanket on the hot side often lets an aluminium panel replace a much heavier steel one.
- Plan inserts: potting compounds also have temperature ratings; specify a high-temperature potting where inserts carry load in hot zones.
How to specify and order heat-exposed aluminium honeycomb
- Temperature profileContinuous and peak temperature, time at each, thermal cycles, and whether the panel is loaded while hot.
- ConstructionBonded core (state node adhesive rating) or brazed panel; facing alloy and thickness; facing adhesive if bonded.
- Core geometryAlloy (3003, 5052, 5056), cell size, foil gauge or density, slice thickness, expanded or unexpanded, perforated or not.
- Panel formatSheet size, thickness, edge closures, inserts and finishing.
- TestingFlatwise compression (ASTM C365), plate shear (ASTM C273) and flatwise tension (ASTM C297), at room and service temperature if required.
- DocumentsMaterial certificates for foil and facings, test reports and conformity to the agreed specification (for example AMS-C-7438 for aerospace core).
Metline supplies aluminium honeycomb core and brazed aluminium panels cut to size, with test reports to the agreed method. For lower-temperature sandwich structures, compare the honeycomb sandwich panel options, and for an overview of every core and panel type see honeycomb core materials and sandwich panels.
References and standards
- SAE AMS-C-7438 – Core Material, Aluminum, for Sandwich Construction
- SAE AMS 4178 – Core, Flexible Honeycomb, Aluminum Alloy, 5052, 350 °F (177 °C)
- ASTM C365 – Flatwise Compressive Properties of Sandwich Cores
- ASTM C273 – Shear Properties of Sandwich Core Materials
- ASM Handbook, Volume 21: Composites – Honeycomb and sandwich structures
High-temperature honeycomb core: frequently asked questions
How hot can aluminium (aluminum) honeycomb get?
Standard adhesive-bonded aluminium core is normally rated to about 177 °C (350 °F), where it keeps roughly two-thirds of its room-temperature strength. Brazed aluminium honeycomb has no adhesive and can run hotter, with the limit set by softening of the alloy; obtain test data for any continuous loaded service above 177 °C.
What honeycomb core withstands the highest temperatures?
Stainless steel and nickel-based alloy cores, joined by welding or high-temperature brazing, are used in the hottest zones such as turbine seals and exhaust structures. Metline supplies only aluminium honeycomb; these are listed for comparison.
Is aramid honeycomb more heat-resistant than aluminium?
Not significantly. Typical phenolic-resin aramid core is also used up to about 177 °C. It is chosen for insulation, radar transparency and toughness rather than higher temperature.
Does brazed aluminium honeycomb outgas?
No organic adhesive is used, so a brazed panel does not release adhesive volatiles when heated, which suits ovens, clean environments and vacuum equipment.
What limits a finished sandwich panel temperature?
The lowest-rated element: node adhesive, facing adhesive, facing material, potting around inserts or edge sealant. Rating the core alone can overstate what the panel will tolerate.
Will aluminium honeycomb burn?
Aluminium is non-combustible, but it melts at roughly 600 – 650 °C depending on alloy, so honeycomb does not carry load in a fire. Fire classification of a panel depends on its adhesives and facings and is tested on the complete product.
Need honeycomb for a hot environment?
Share the temperature profile, loads and panel size. We will advise whether bonded core or brazed aluminium panels will work and quote them.
