The versatility of aluminum composite lies not only in its lightness, but also in the variety of assembly techniques available. Choosing the right joining system is crucial to ensure the structural stability of the façade and its long-term resistance to wind loads and thermal changes.
The advice of façade installation experts allows the selection of the fastening technology that best suits the technical requirements of the project, whether by means of mechanical or chemical anchors.
Chemical adhesion and bonding systems
The use of adhesives provides a clean, aesthetically pleasing finish, ideal for areas where visible fasteners are not desired. However, the chemistry of the materials plays a crucial role. When bonding aluminum to other substrates, it is vital to use highly elastic adhesives, usually polyurethane-based, that absorb the stresses caused by differential expansion.
Below, we detail the compatibility according to the type of panel core:
| Core Type | Recommended Adhesion Method | Technical Considerations |
| Polyethylene (PE) | Welding or mechanical fastening | Low surface energy; standard chemical bonding usually fails. |
| Polyurethane (PUR) | Butt or structural adhesives | Resists well, but the shear load must be monitored. |
| Mineral (FR/A2) | Elastic mounting adhesives | Ideal for indoor or moderate load areas. |
The hot air welding technique
To achieve tight and homogeneous joints, especially in thermoplastic core panels, welding is a robust option. This process requires specific machinery that injects air at controlled temperatures (between 260 and 270 °C) to melt the core and filler wire, creating a solid fusion.
Critical steps for effective welding:
- Edge preparation: It is mandatory to bevel the ends of the parts to accommodate the welding wire.
- Cleaning: On PE cores, pre-sanding improves physical adhesion.
- Time of execution: It must be welded within 24 hours after cutting to avoid oxidation of the surfaces.
- Finishing: After cooling, the excess material is removed with a blade to leave a flat surface.
Mechanical fastening: Screws and Rivets
The most widespread method in ventilated facades is mechanical bonding due to its reliability and ease of inspection. The correct fastening of composite panels by means of screws or rivets requires taking into account the linear expansion of aluminum (approx. 2.4 mm per meter with a thermal jump of 100°C).
To avoid façade pathologies, the fasteners must meet stringent quality standards:
- Material: Always use stainless steel to prevent galvanic corrosion. Galvanized screws lose their coating when threaded and rust within a few years.
- EPDM washers: Fundamental to seal the hole and prevent water seepage.
- Clearance: Holes in the panel should be slightly larger than the screw diameter to allow for movement of the material without bending.
- Geometry: Double-threaded screws with hardened drill point facilitate installation on metal substructures.
Importance of assembly management
A common mistake in installation, regardless of the joining method, is to ignore the directionality of the panel. Aluminum composite usually has a paint finish applied in a specific direction. If adjacent panels are installed in opposite orientations (rotated 90° or 180°), the light reflection will vary, creating a visual effect of “patching” or hue change, even though the color is identical. It is essential to follow the arrows marked on the protective film.
Frequently asked questions about composite panel fastening
Can I use regular glue to join the panels together?
Not recommended. You must use specific elastic polyurethane adhesives for metals that withstand vibrations and temperature changes, prior adhesion test.
What happens if I overtighten the screws?
Excessive tightening blocks the panel and prevents its natural expansion. This causes the surface to bulge or deform (“pillow effect”) when the temperature rises.
Is the rivet or the screw better?
Both are valid. The rivet is faster and more economical for aluminum substructures, while the screw allows for easy disassembly if necessary.
Why can’t any composite panel be welded?
Only those with a thermoplastic core (such as polyethylene) allow fusion. Honeycomb or mineral core panels require adhesives or mechanical fasteners.
Do the screws rust over time?
If you use quality stainless steel screws (A2 or A4), they will not rust. If you use cheap galvanized steel, corrosion will appear in 2 to 5 years.
What are expansion joints?
These are the spaces left between panels (or in the fixing holes) so that the material can expand with the heat without colliding or deforming.
At Panel Composite we master the technique. These joints are part of our Alucobond mounting systems for facades.