A sandwich panel is a three-layer structural panel made up of two thin, stiff outer skins bonded to a lightweight core material in between. The result is a panel that carries bending loads through its skins while the core resists shear forces, delivering high stiffness and strength at a fraction of the weight of solid steel or wood. The questions below unpack how sandwich panels are built, how they perform, and what to look for when specifying them for commercial vehicle or structural applications.
This article covers the broader sandwich panel market. Compoform’s range is limited to PP honeycomb and PET foam cores for commercial vehicles and scaffolding.
What are sandwich panels made of?
A sandwich panel consists of three components: two outer face skins, a core material, and an adhesive or bonding layer that holds them together. The skins carry tensile and compressive loads. The core separates the skins and transfers shear between them. The bond between skin and core is what makes the whole system work as a single structural unit.
Face skins are typically made from fibre-reinforced thermoplastics, steel, or aluminium, depending on the application. In composite sandwich panels designed for transport and structural use, glass-fibre-reinforced polypropylene (glass-fibre PP) is a common choice. Skins can be built up in multiple plies; two-ply or four-ply laminates are typical, with fibres oriented in different directions to balance strength across axes. A cross-ply arrangement, for example, places fibres at 0° and 90° in alternating layers to distribute load in both directions.
Core materials vary widely across the market. The two most common in high-performance composite panels are:
- PP foam cores: Oriented polypropylene foam, available in a range of densities. Lower-density foam reduces weight; higher-density foam increases compressive strength and stiffness.
- PP honeycomb cores: A tubular cell structure that delivers very high stiffness-to-weight ratios, making it well suited to floor panels and structural decking where point loads are a concern.
Surface finishes are applied to the outer face of the skins. A white PET film gives a clean, paintable surface for wall cladding. A black anti-skid finish is used on floor panels and scaffolding boards where grip underfoot matters.
How does a sandwich panel achieve its strength?
A sandwich panel achieves its strength through the separation of its two stiff skins by a lightweight core. When a panel bends under load, one skin goes into tension and the other into compression. Placing the skins as far apart as possible, separated by the core, maximises the panel’s resistance to bending without adding proportional weight. This is the same structural principle as an I-beam.
The core does not carry bending loads directly. Its job is to resist shear forces between the two skins and to keep them at a fixed distance from each other. If the bond between skin and core fails, the panel loses its composite action and the skins buckle independently, which is why the quality of the skin-to-core bond is as important as the properties of the materials themselves.
Skin architecture plays a significant role in how load is distributed. A four-ply glass-fibre laminate with fibres oriented in multiple directions resists loads from different angles, which matters in floor panels that experience both point loads and distributed loads simultaneously. The fibre content of the skin, typically around 66 to 67% glass fibre by weight in high-performance thermoplastic panels, directly determines tensile stiffness and strength.
Core density also affects structural performance. A denser foam core resists compression more effectively, which is relevant for floor panels under concentrated loads. A PP honeycomb core, with its tubular cell geometry, provides very high shear stiffness relative to its weight, making it the preferred choice for applications where deflection under load must be minimised.
What types of sandwich panels are there?
Sandwich panels are categorised primarily by their core material and skin type. The core determines the panel’s weight, stiffness, and load-bearing capacity. The skin determines surface durability, tensile strength, and finish. Different combinations suit different applications.
Core types
The most common core materials in the broader market include foam cores (polypropylene, polyurethane, or PET-based), honeycomb cores (polypropylene, aluminium, or paper), and rigid insulation cores used in building panels. In composite panels for transport and structural applications, PP foam and PP honeycomb are the dominant choices because both are fully thermoplastic, recyclable, and compatible with glass-fibre thermoplastic skins.
Skin types
Skins range from thin steel or aluminium sheets in construction panels to glass-fibre- or carbon-fibre-reinforced thermoplastic laminates in composite panels. Thermoplastic skins offer impact resistance, chemical resistance, and the ability to be thermoformed or welded. The number of plies and fibre orientation in the laminate determine how the skin performs under load in different directions.
Panel thickness across the market ranges from around 10 mm for thin structural panels up to 150 mm or more for insulated building panels. In composite panels for commercial vehicles and scaffolding, thicknesses between 11 mm and 30 mm cover most structural requirements.
What are sandwich panels used for?
Sandwich panels are used wherever a structure needs to be stiff, strong, and light at the same time. The most common sandwich panel applications in transport and construction are commercial vehicle bodies, structural flooring, wall cladding, and scaffolding boards, but the principle applies across any industry where dead weight is a cost and structural performance is non-negotiable.
In commercial transport, sandwich panels replace steel or plywood in truck body side walls, rear doors, and floor panels. A lighter body structure means more payload capacity within legal gross vehicle weight limits. In 2026, this weight argument extends beyond payload: lighter body structures extend battery range in electric trucks and vans. Every kilogram of structural dead weight reduces range per charge, making weight reduction a range argument, not just a payload argument. This is a standard procurement question from EV fleet buyers.
Scaffolding boards are another high-demand application. Composite sandwich panels rated to EN 12811 load class 4 can replace timber boards with a product that does not rot, warp, or absorb water, and that weighs significantly less, reducing fatigue for workers handling boards at height.
Other applications include:
- Trailer side walls and floors
- Cargo box panels for refrigerated transport
- Façade cladding panels for buildings
- Caravans and mobile homes
- Horse vans and specialist vehicle bodywork
How do sandwich panels compare to steel or wood panels?
Sandwich panels are significantly lighter than steel and more durable than wood, while matching or exceeding both in structural performance for most transport and flooring applications. The trade-off is a higher unit cost, but when you account for the full service life, the economics shift in favour of composite panels.
Against steel, the weight advantage is the primary argument. A composite sandwich panel can deliver comparable bending stiffness at a fraction of the mass. For a truck body builder, that difference translates directly into additional payload capacity or extended battery range in an electric vehicle, both of which have measurable commercial value per vehicle per year.
Against plywood, the durability argument is more compelling than the weight argument. Plywood floors in heavy transport typically last three to five years before they need replacing. A composite sandwich floor, properly specified, lasts twelve years or more. Over a fifteen-year vehicle life, that eliminates two to three replacement cycles. Once you add panel cost, installation labour, and vehicle downtime for each replacement, the composite floor is cheaper per year of service, even at a higher unit price.
Steel and wood also absorb moisture, corrode, or rot when exposed to repeated wash-downs, chemical spills, or outdoor weathering. Thermoplastic composite panels resist all three. Edge sealing and edge bending protect the core from moisture ingress, which is relevant for both scaffolding boards and truck floors that are washed down regularly.
What should you look for when choosing a sandwich panel?
When choosing a sandwich panel, the most important factors are core type, skin architecture, panel dimensions, surface finish, and the standards the panel has been tested against. Getting any one of these wrong for your application means either over-engineering (adding unnecessary cost and weight) or under-engineering (risking structural failure).
- Core type and density: Match the core to the load type. PP honeycomb handles concentrated point loads well. PP foam in higher densities suits applications with distributed loads and compressive demands. Confirm the density range available and whether it suits your load calculations.
- Skin architecture: A two-ply skin suits lighter wall cladding applications. A four-ply skin is appropriate for floor panels and scaffolding boards where tensile and bending demands are higher. Check whether the fibre orientation matches the primary load direction in your application.
- Panel dimensions: Standard panel sizes rarely match production requirements exactly. Confirm whether the supplier can cut to your exact dimensions, and whether edge sealing or edge bending is available as part of the supply.
- Surface finish: A PET film surface suits wall panels and interior cladding. An anti-skid surface is required for floors and scaffolding boards where slip resistance is a safety requirement.
- Test standards: For European applications, look for panels tested to EN ISO 527 for tensile performance, ISO 14125 for flexural properties, and EN 12811 for scaffolding load classes. Fire classification under EN 13501-1 is relevant for enclosed vehicle bodies and building applications.
- Recyclability: For OEMs subject to EU End-of-Life Vehicle (ELV) Directive requirements, fully thermoplastic panels, where both skin and core are polypropylene-based, simplify end-of-life compliance. This is increasingly a procurement requirement, not just a preference.
Specifications vary by customer and application. Always confirm the specific requirements of your project before finalising a panel configuration.
How Compoform Helps You Specify the Right Sandwich Panel
We manufacture thermoplastic sandwich panels using PP honeycomb and PET foam cores, with glass-fibre-reinforced thermoplastic skins in two-ply and four-ply configurations. Our panels are produced at our facilities in Beek and Ospel, the Netherlands, and are available in custom dimensions up to 13,500 mm × 2,950 mm, cut to your exact specification.
Here is what working with us looks like in practice:
- Application review: We review your design and load requirements before recommending a panel configuration, core type, density, skin architecture, thickness, and surface finish.
- Structural validation: Our panels are tested to European standards including ISO 14125 for flexural performance and EN 12811 for scaffolding load classes. A 10.5 mm Compoform panel has achieved EN 12811 load class 4 with no support underneath, a result we can share with your engineering team.
- Self-supporting floor panels: A 30 mm PP sandwich panel floor is self-supporting, removing the need for an aluminium subframe. This eliminates a production step and reduces cost for truck body builders.
- Edge protection: Edge sealing and edge bending are available to protect the core from moisture and UV, relevant for scaffolding boards and truck floors washed down regularly.
- ELV compliance support: Our fully thermoplastic panels simplify end-of-life compliance under the EU ELV Directive for OEMs who need to demonstrate recyclability.
- Ongoing support: We stay involved through integration, any issues that arise, and design iteration, not just the initial order.
If you are specifying panels for truck body flooring or scaffolding applications and want to review the right configuration for your production requirements, contact our engineering team to start the conversation.