Structural Bonding in Transport: Bodywork, Rail and Marine

Already adopted across 35% of the world's rail fleet, structural bonding is now establishing itself as the essential productivity lever for overcoming the weight and fatigue limits of traditional mechanical fasteners.

Yet many manufacturers remain loyal to welding or bolting, holding back the acceleration of their own production rates.

Here is a breakdown of the adhesive solutions deployed and recommended by ACROM in bodywork, rail and marine, combining lightness, safety and profitability.

Why adhesive is replacing mechanical fasteners

Switching to a bead of adhesive changes the very structure of vehicles. Adhesive does more than join two parts: it distributes loads, absorbs impacts and seals the assembly in a single pass.

Reducing cycle times and hidden costs

An assembly made by riveting or bolting requires multiple operations: marking out, drilling, deburring, fitting the insert, then applying a sealant to prevent water ingress. Bonding removes these steps. Operators lay down the bead, position the part, and the assembly is complete.

The fast curing of today's adhesives allows sub-assemblies to be handled within minutes. Lower noise levels in the workshop and fewer rejects caused by drilling errors have a direct impact on the cost per part.

Lighter structures and mechanical integrity

Drilling a chassis or a panel inevitably creates a mechanical weakness. Traditional fasteners concentrate stresses on an extremely small area, which encourages cracks to appear under vibration.

Adhesive distributes the load (tension, shear, peel) across the entire contact surface. This distribution makes it possible to use thinner, lighter materials (aluminium, composites, thermoplastics) without the risk of tearing. In transport, every kilogram saved translates into a higher payload or lower fuel consumption.

Sector requirements: Bodywork, Rail and Marine

Each environment imposes its own physical limits. The choice of chemistry must meet extremely strict specifications.

Industrial bodywork: mastering sandwich panels

The walls of refrigerated trucks and utility vehicles combine polyester or aluminium skins with insulating cores. These large surfaces endure continuous road impacts and sharp temperature swings.

To keep the panels bonded without delamination, reactive one-component polyurethane adhesives such as ACROBOND PU 101 or two-component PU adhesives such as ACROBOND PU 253 provide fast, adjustable curing. For the structural assembly of chassis elements (steel, aluminium, composite), the two-component polyurethane ACROBOND PU 211/30 delivers high mechanical strength while absorbing the micro-deformations of the road.

Rail: resistance to dynamic fatigue

A train runs for decades. Its assemblies withstand dynamic loads and vibrations that destroy poor-quality welds. On top of this, reducing noise and vibration in the cab (NVH standards) is an essential comfort criterion.

ACROBOND PU 290/08 is formulated on a polyurethane base. It offers remarkable resistance to vibration fatigue. Using it ensures the integrity of the structure and the safety of passengers in the face of mechanical ageing.

Marine: watertightness and saline environment

At sea, salt, water and ultraviolet rays attack materials constantly, while the swell imposes constant torsion on the hull.

Upstream, during the manufacture of polyester hulls, the ACROBOND® CS 60 SPRAY aerosol holds the fibreglass precisely in place before resin infusion, without creating structural defects. When bonding cable glands in vertical application on hulls, the chosen adhesive must offer enough thixotropy to prevent any sagging on the substrate, together with fast grab. ACROBOND A 232/2 is a particularly well-suited solution for rapid assembly operations in series production.

Recommended technologies at a glance

Managing hostile environments and adhesive chemistry

The success of a bonded joint relies on mastering the physical stresses that act on the vehicle throughout its service life.

Thermal expansion and galvanic corrosion

Bonding an aluminium panel to a steel structure raises two issues.

First, these metals expand at different rates under the sun, which pops rivets or shears welds. Adhesive acts as an elastic buffer that absorbs this dimensional difference.

Second, direct contact between two dissimilar metals in a humid environment causes galvanic corrosion that eats away at the aluminium. The bead of adhesive forms a watertight dielectric barrier that permanently blocks this phenomenon.

Choosing the chemistry according to the substrate

The technology is dictated by the rigidity required. Two-component polyurethanes provide strong structural hold. Conversely, MS polymers favour flexibility and sealing. Whatever the technology, adhesion depends on substrate preparation: thorough degreasing with suitable solvents (the ACRODIS® range) and the application of a primer are often required to make the bond last.

Reliable dispensing process and quality control

A product data sheet guarantees nothing if the application process is not mastered on the assembly line.

ACROM technical expertise

Manual, pneumatic or robotic dispensing requires stable product viscosity. At ACROM, we define your entire protocol:

• Validation of surface treatment (abrasion, cleaning).
• Selection of dispensing equipment (pneumatic or electric Medmix-type guns, choice of static mixers according to the ratio).
• Setting of open times and curing speed to match your cycle times.

Traceability and standards compliance

In transport, traceability is mandatory. To meet rail and automotive requirements, we oversee the implementation of strict protocols: visual inspection of bead consistency, recording of batch numbers, logging of workshop temperatures and regular destructive testing (peel and shear) to validate the cohesion of assemblies through external laboratories.

Secure your assembly lines

Adopting industrial structural bonding lightens your vehicles and speeds up your production times. Leave no variable to chance. Our team welcomes you to La Seguiniere to test your own substrates (aluminium, steel, composites) and define the exact chemistry that will increase your workshop throughput. Contact the ACROM technical team.