Sandwich panels reduce payload dead weight in freight vehicles by replacing heavy steel or plywood body panels with a lightweight composite structure that carries the same structural loads at a fraction of the mass. The weight saving comes from the panel’s construction: stiff fibre-reinforced skins bonded to a low-density core deliver high strength-to-weight ratios that solid materials cannot match. The questions below unpack how that works in practice, what gains are realistic, and what to consider when specifying panels for your vehicle build.
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.
How much dead weight do conventional freight vehicle panels actually add?
Conventional freight vehicle body panels made from steel or plywood contribute significant structural dead weight that directly reduces the payload a vehicle can legally carry. A steel side wall panel can weigh anywhere from 15 to 25 kilograms per square metre depending on gauge, while structural plywood used for truck floors typically runs between 8 and 14 kilograms per square metre. Across a full trailer body, that accumulates quickly.
A standard curtainsider trailer body uses floor panels, side walls, a roof, and a front wall. When those surfaces are built from steel or hardwood plywood, the body structure alone can account for several hundred kilograms of dead weight before a single kilogram of cargo is loaded. Every kilogram of that structural mass is a kilogram subtracted from the vehicle’s legally permitted gross vehicle weight, which in Europe is typically capped at 40 tonnes for a standard articulated combination.
For fleet operators and truck body builders, this is not an abstract engineering concern. It is a direct commercial constraint. A vehicle that carries 200 kilograms less cargo per trip, running five days a week, represents a measurable reduction in revenue-generating capacity over a vehicle’s working life. The pressure to reduce structural dead weight has intensified further as fleet operators transition to electric trucks, where battery packs already consume a significant portion of the gross weight allowance before the body is even fitted.
How does a sandwich panel’s construction make it lighter than solid materials?
A sandwich panel achieves its low weight through a structural principle: two thin, stiff face skins are bonded to a lightweight core material, creating a composite structure that resists bending loads far more efficiently than a solid panel of equivalent mass. The core separates the skins, increasing the panel’s second moment of area without adding proportional weight. This is the same principle that makes an I-beam stiffer than a solid rectangular bar of the same cross-sectional area.
The skins carry the tensile and compressive stresses generated by bending loads. In thermoplastic sandwich panels, these skins are typically glass-fibre-reinforced polypropylene laminates, which deliver high stiffness and strength at low areal weight. The core, whether PP honeycomb or oriented PP foam, carries the shear forces between the skins while contributing very little mass. PP honeycomb cores, for example, consist largely of air enclosed within a tubular cell structure, so the bulk of the panel volume adds almost no weight.
The result is a panel that can span structural distances, resist point loads, and maintain dimensional stability under temperature cycling, while weighing substantially less than steel or plywood of comparable structural performance. The skin architecture also matters: a cross-ply laminate, with fibres oriented at 0° and 90°, distributes load-bearing capacity in both directions, which is useful for wall panels that may be installed in either orientation. A unidirectional or multi-ply arrangement concentrates stiffness along the primary load axis, which suits floor panels where the dominant load direction is predictable.
What payload gains can freight operators realistically expect from switching to composite panels?
Realistic payload gains from switching to composite sandwich panels depend on the specific vehicle type, the panels being replaced, and the number of surfaces converted. As a general direction, replacing steel or plywood body panels with thermoplastic sandwich panels typically reduces body structure weight by a meaningful margin per surface, and the cumulative effect across a full trailer body can reach several hundred kilograms. Any specific figure needs to be validated against the actual panel specifications for your build.
For truck body builders, the floor is often where the largest single gain is available. A structural plywood floor on a rigid truck body or trailer can be replaced with a self-supporting composite floor panel that requires no aluminium subframe underneath. Eliminating the subframe removes additional dead weight on top of the panel weight saving itself, and it also simplifies the assembly process. A 30 mm PP sandwich panel floor, for instance, is self-supporting in standard truck body spans, which removes a production step and reduces both material cost and total structure weight simultaneously.
Side wall panels offer further savings. Composite wall panels with PP foam cores are substantially lighter than steel equivalents while providing comparable rigidity for the loads a side wall actually experiences in service. Roof panels and front walls follow the same logic. When you convert multiple surfaces, the gains compound. For fleet operators running high-utilisation vehicles, even a modest increase in legal payload per trip translates into measurable revenue improvement over a vehicle’s working life.
For fleets transitioning to electric trucks and vans, the argument extends beyond payload. Lighter body structures extend battery range per charge. Every kilogram of structural dead weight that remains in the body is a kilogram that reduces the distance the vehicle can travel before recharging. In 2026, this is a standard procurement question from EV fleet buyers, and it means weight reduction is simultaneously a payload argument and a range argument. Specifying lightweight composite panels addresses both concerns with a single material decision.
Do lightweight sandwich panels compromise structural strength or durability?
Lightweight sandwich panels do not compromise structural strength when correctly specified for the application. The sandwich construction principle achieves high stiffness and load-bearing capacity through geometry rather than mass, and fibre-reinforced thermoplastic skins deliver tensile and flexural performance that meets or exceeds the structural requirements of truck body walls, floors, and roofs. The relevant question is not whether composite panels are strong enough, but whether they are specified correctly for the load case.
Durability is where composite panels often outperform the materials they replace. Thermoplastic sandwich panels do not rot, delaminate from moisture ingress, or corrode. Plywood floors in heavy transport typically require replacement every three to five years under hard use. A thermoplastic composite floor, by contrast, can last twelve years or more in the same environment, eliminating two or three replacement cycles over a vehicle’s working life. When you account for panel cost, installation labour, and vehicle downtime during replacement, the composite is cheaper per year of service even at a higher unit price.
Impact resistance is a legitimate consideration for freight applications, where panels are exposed to loading equipment, shifting cargo, and regular wash-down cycles. Glass-fibre-reinforced thermoplastic skins handle impact loads well, and edge sealing protects the core from moisture and UV exposure at cut edges, which is relevant for floor panels washed down regularly. Structural performance should always be validated against the specific load requirements of the application, using European standards such as ISO 14125 for flexural properties and EN ISO 527 for tensile performance, rather than relying on generic material claims.
Which freight vehicle applications benefit most from sandwich panel weight reduction?
The freight vehicle applications suited to sandwich panels that benefit most from sandwich panel weight reduction are those where structural panels cover large surface areas, where the replaced material is heavy relative to its structural contribution, and where payload utilisation is commercially important. Trailer floors, truck body side walls, cargo box roofs, and van body panels all meet these criteria.
Trailer and truck body floors
Floors carry the highest structural demands in a freight body, supporting both distributed cargo loads and concentrated point loads from forklift tyres and pallet feet. A composite floor panel with a PP honeycomb core delivers the compressive and bending performance needed for these loads while weighing significantly less than hardwood plywood. The self-supporting capability of correctly specified composite floor panels also eliminates the need for a separate subframe, which removes additional dead weight and simplifies body construction.
Side walls and roof panels
Side walls and roofs cover large areas but carry lighter structural loads than floors, which means the core density and skin weight can be optimised for minimum mass without sacrificing performance. PP foam core panels with glass-fibre-reinforced skins are well suited to these surfaces. The weight saving per square metre is consistent, and across the full side wall and roof area of a trailer or rigid truck body, the cumulative reduction is substantial. Wall panels with white PET-film surfaces also provide a finished interior surface without additional lining materials, which removes further weight and assembly steps.
What should vehicle manufacturers consider when specifying sandwich panels for payload optimisation?
Vehicle manufacturers specifying sandwich panels for payload optimisation need to consider load requirements, panel dimensions, core selection, skin architecture, and the interaction between the panel and the surrounding vehicle structure. Getting these decisions right at the design stage avoids costly corrections later and ensures the weight saving is not offset by structural underperformance or integration problems.
Load case definition is the starting point. Floor panels, wall panels, and roof panels each face different load types and magnitudes. A floor panel must resist concentrated point loads from forklifts and distributed loads from cargo, while a side wall primarily resists racking and impact. The core material, density, and skin layup should be matched to the actual load case, not selected generically. PP honeycomb cores at 140 kg/m³ deliver high compressive and bending performance suited to floor applications, while lower-density PP foam cores are appropriate for wall panels where the load demands are less severe.
Panel dimensions and integration matter practically. Composite panels can be produced in large formats, up to 13,500 mm in length, which reduces the number of joints in a body structure. Fewer joints mean less sealing, fewer potential failure points, and a cleaner assembly process. Specifying panel dimensions that align with your body structure avoids unnecessary cutting waste and ensures edge conditions are managed correctly from the outset.
Surface finish and edge treatment affect both function and longevity. Anti-skid surfaces are relevant for floor panels in cargo environments. White PET-film surfaces suit interior wall cladding. Edge sealing at cut edges protects the core from moisture and UV exposure, which is particularly important for panels used in wash-down environments or exposed to weather during loading operations.
Total cost of ownership should frame the specification decision, not unit price alone. A composite panel that lasts twelve or more years in service eliminates the replacement cycles that plywood requires, and a self-supporting floor panel removes the cost of a separate subframe. These are concrete cost reductions that should be calculated against the panel price when making the specification decision.
How Compoform Helps You Reduce Payload Dead Weight
We work with truck body builders, trailer manufacturers, and fleet operators across Europe to design and produce thermoplastic sandwich panels that directly address structural dead weight without compromising load performance. Our panels use PP honeycomb or PET foam cores with glass-fibre-reinforced thermoplastic skins, and every configuration is engineered for the specific application rather than selected from a generic catalogue.
- Custom panel dimensions: Panels are produced to your exact specification, up to 13,500 mm × 2,950 mm, reducing joints in the body structure and simplifying assembly.
- Self-supporting floor panels: Our 30 mm PP honeycomb floor panels are self-supporting in standard truck body spans, eliminating the need for an aluminium subframe and removing both cost and dead weight from your build.
- Application-matched core selection: We specify PP honeycomb or PET foam cores at the density and thickness your load case requires, using ISO 14125 and EN ISO 527 as the reference standards for performance validation.
- Long service life: Thermoplastic composite floors last 12 or more years in heavy transport use, eliminating two to three plywood replacement cycles over a vehicle’s life. Over a 15-year vehicle life, that removes multiple rounds of panel cost, installation labour, and vehicle downtime.
- EV fleet compatibility: For operators transitioning to electric trucks, we can help you quantify the combined payload and range benefit of switching to composite body panels, which is increasingly a procurement requirement from EV fleet buyers.
Before production, we review your body design, assess the load requirements for each panel position, and recommend the configuration that delivers the weight saving you need without introducing structural risk. If there are integration challenges in your assembly process, we identify them at the design stage rather than after panels are on the production floor.
To discuss your specific vehicle build and what panel configuration would work for your application, get in touch with our engineering team directly.