OEM manufacturers specify sandwich panels by matching panel construction to the structural, weight, and surface demands of each vehicle zone. The right specification depends on whether a panel will serve as a floor, wall, or roof, and on the load class, surface finish, and dimensional constraints that apply to that vehicle type. The questions below unpack how those decisions differ across trucks, trailers, coaches, and caravans.

Note: This article covers the broader sandwich panel market. Our range at Compoform is limited to PP honeycomb and PET foam cores for commercial vehicles and scaffolding.

What performance requirements drive sandwich panel selection in vehicles?

Sandwich panel selection in vehicles is driven by four core performance requirements: structural load capacity, weight, surface durability, and dimensional stability under temperature cycling. Every other specification decision flows from how those four factors are balanced for a given vehicle type and application zone.

Load capacity determines the core material and density. A floor panel in a curtainsider trailer must support distributed pallet loads and point loads from forklift tines, which demands a stiffer, higher-density core than a sidewall panel that only needs to resist wind pressure and minor impact. Specifying a core that is too light for the load case leads to core compression or skin delamination over time.

Weight is the second constraint, and in 2026 it carries a dual commercial argument. Every kilogram saved in body structure adds a kilogram of revenue-generating payload under European gross vehicle weight regulations. For fleet operators transitioning to electric trucks and vans, the argument extends further: lighter body structures extend battery range per charge. Weight reduction is now a range argument as much as a payload argument, and EV procurement teams treat it as a standard specification question.

Surface durability covers abrasion resistance, moisture resistance, and the ability to withstand repeated wash-down cycles. Floors need anti-skid surfaces and sealed edges. Walls need UV-stable finishes that retain colour and gloss over years of outdoor exposure. Dimensional stability matters because vehicle bodies experience significant temperature swings, and panels that expand or contract unevenly cause joint failures and rattles over time.

How do panel specifications differ between trucks and trailers?

Truck body panels and trailer panels share the same basic sandwich construction but differ significantly in thickness, core density, and surface specification. Truck bodies prioritise low tare weight and interior finish quality, while trailers prioritise structural rigidity and floor load capacity under repeated heavy-duty use.

Truck body panel priorities

Truck body builders typically specify thinner wall panels with lower-density cores because the body is mounted on a rigid chassis that carries the structural load. The walls and roof primarily need to resist wind pressure, impact, and weather. A white PET-film surface finish on the interior is common because it provides a clean, reflective surface without additional lining. The cross-ply skin architecture is well suited here because it equalises mechanical properties in both directions, allowing panels to be installed in either orientation without performance loss.

For the floor, the specification changes sharply. Truck body floors must support repeated loading from pallet trucks and hand trucks. A PP honeycomb core at higher density, combined with a 4-ply glass-fibre skin and an anti-skid surface, delivers the bending and compressive performance needed. A 30 mm PP sandwich floor panel is self-supporting, which means no aluminium subframe is required beneath it. That removes a production step and reduces both cost and weight for the body builder.

Trailer panel priorities

Trailers face more demanding structural conditions. Curtainsider and box trailer floors must handle forklift entry, high point loads, and years of heavy-duty cycling. Core density requirements are therefore higher, and panel thickness is typically greater than in a comparable truck body floor. Trailer sidewalls also need to resist lateral racking loads that are less relevant in a rigid truck body. Dimensional accuracy matters more in trailers because panels often span longer distances between structural members, and any bow or twist in the panel creates assembly problems at scale.

What sandwich panel properties matter most for bus and coach bodybuilding?

For bus and coach bodybuilding, the properties that matter most are fire performance, acoustic damping, surface finish quality, and low weight. Bus and coach bodies are passenger environments, which introduces regulatory requirements around fire behaviour that do not apply to freight vehicles.

Fire performance is specified under EN 13501-1 in European markets. Panel skins and cores must meet the required reaction-to-fire classification for the interior zone in which they are installed. This narrows the range of viable core and skin combinations compared to freight applications.

Acoustic performance is relevant because passengers notice vibration and noise transmission through the body panels. Sandwich panels with foam cores tend to offer better acoustic damping than honeycomb cores of equivalent stiffness, which is a factor worth considering during specification. Surface finish quality matters because interior panels are visible to passengers and must retain their appearance over years of service, including cleaning with commercial detergents.

Weight remains important in coach bodybuilding, particularly as operators move toward electric and hybrid drivetrains. A lighter body structure directly extends range per charge, and coach operators evaluating electric vehicles increasingly factor body weight into their total cost of ownership calculations alongside energy costs and charging infrastructure.

How do caravan and motorhome manufacturers specify composite panels differently?

Caravan and motorhome manufacturers specify composite panels with a stronger emphasis on thermal insulation, long-term weathering resistance, and interior surface aesthetics than commercial vehicle manufacturers do. The panels must perform as both structural and insulating elements across decades of outdoor exposure.

Thermal performance is a primary driver. Caravan walls and roofs need to limit heat transfer in both summer and winter conditions, which influences core material selection and thickness. Thicker panels with lower-density foam cores can deliver better thermal resistance while keeping weight manageable. The thermal conductivity of the core is a specification input that commercial vehicle engineers rarely prioritise but caravan engineers treat as a key parameter.

Weathering resistance is the second major differentiator. Caravan bodies are parked outdoors for extended periods and exposed to UV radiation, rain, and temperature cycling over many years. Panel skins with UV-stable surface finishes are important here. A white PET-film surface with a high UV resistance rating maintains colour and gloss over thousands of hours of outdoor exposure, which matters both for appearance and for the resale value of the finished vehicle.

Interior aesthetics also carry more weight in caravan specification than in freight applications. The interior surface of a caravan wall panel is often the finished surface visible to the end user, so colour consistency, gloss level, and surface smoothness are part of the specification rather than secondary considerations.

Which sandwich panel core and skin combinations suit which vehicle applications?

The right core and skin combination depends on whether the panel is carrying bending loads, compressive loads, or primarily serving as a weather barrier, and on the surface requirements of the application zone. Different vehicle applications and panel use cases call for different combinations.

For truck and trailer floors, a PP honeycomb core at higher density paired with a 4-ply glass-fibre skin and an anti-skid surface finish delivers the bending strength and compressive resistance needed for forklift and pallet loading. The honeycomb geometry provides a high stiffness-to-weight ratio, which is why it is preferred over foam cores in high-load floor applications.

For truck body and trailer sidewalls, a PP foam core at lower density with a cross-ply or 2-ply skin and a PET-film surface finish is the standard approach. The foam core provides adequate stiffness for lateral loads while keeping panel weight low. The cross-ply skin architecture distributes load evenly in both directions, which simplifies installation and reduces the risk of orientation errors during body assembly.

For caravan and motorhome walls and roofs, a foam core with controlled density and a UV-stable surface finish is the preferred combination. The foam core contributes to thermal insulation, and the surface finish must maintain its appearance over years of outdoor exposure. Skin thickness and layup are calibrated to the structural demands of the specific panel zone rather than to heavy load-bearing requirements.

For coach and bus interior panels, the combination must satisfy fire classification requirements under EN 13501-1 alongside the structural and surface requirements. This often means specifying skins and cores that have been tested and certified for the relevant fire class, which limits the available combinations compared to freight applications.

When should OEMs request custom panel dimensions instead of standard sizes?

OEMs should request custom panel dimensions when standard sizes create unnecessary waste, introduce assembly joins that compromise structural integrity, or require secondary machining that adds cost and lead time. For most mid-volume OEM production runs, custom dimensions deliver a better outcome than cutting down standard sheets.

The most common trigger for custom dimensions is body length. Commercial vehicle bodies are built to specific internal dimensions that rarely align with standard panel widths or lengths. Cutting a standard panel to fit introduces a cut edge that must be sealed to protect the core from moisture ingress, adds a production step, and generates material waste. Ordering panels cut to the exact body dimension eliminates all three problems.

A second trigger is structural continuity. A floor or wall panel that runs the full length of a body section without a join is structurally superior to two panels butted together. In trailer floors subject to repeated heavy loading, joins are potential weak points. Specifying a single panel that spans the full floor section removes that risk.

A third trigger is surface finish at the edge. When a panel edge is visible in the finished vehicle, a factory-finished edge is cleaner and more durable than a cut edge that has been sealed on-site. This matters in caravan interiors and coach passenger compartments where the finish quality is part of the product specification.

Panels are available in custom dimensions cut to your exact specification, up to 13,500 mm x 2,950 mm. For production runs where the same dimension repeats across every unit, the cost of custom sizing is recovered quickly through reduced waste and faster assembly.

How Compoform Helps OEMs Specify the Right Sandwich Panel

We work with truck body builders, trailer manufacturers, and specialist vehicle OEMs across Europe to translate application requirements into panel specifications that perform in production and in service. That means reviewing your design before panels are ordered, not after a problem appears on the assembly line.

Here is what that looks like in practice:

• Application review: We assess the load case, surface requirements, and dimensional constraints for each panel zone in your vehicle design, and recommend the core type, density, skin architecture, and thickness that match those requirements.
• Custom dimensions to your specification: Panels are produced to your exact dimensions on our 72-metre double belt press, up to 13,500 mm x 2,950 mm x 150 mm, so you receive panels ready to fit without secondary cutting or edge sealing on your line.
• Core and skin selection: We produce panels with PP honeycomb and PET foam cores across a range of densities, combined with glass-fibre skin architectures optimised for your specific load and surface requirements.
• Lifecycle argument support: We help you build the TCO case for composite panels versus steel, wood, or plywood, including lifespan comparisons and payload or range calculations relevant to your customers’ fleet decisions.
• Ongoing production support: We stay involved through integration, iteration, and any issues that arise during your production run, not just at the point of initial order.

Thermoplastic sandwich panels from our production line in Ospel, the Netherlands, are 100% European-made and delivered on customised pallets sized to your production flow. If you are reviewing a new vehicle design or replacing an existing material specification, speak with our application engineers about panel configuration that fits your assembly process and your customers’ performance requirements.

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