Sandwich panels perform well under impact because their layered construction distributes and absorbs energy across multiple materials rather than concentrating stress at a single point. The stiff outer skins resist penetration while the core material deforms to absorb energy. Performance varies significantly depending on skin material, core type, thickness, and the nature of the impact itself.
The sections below work through the specific questions that matter most to engineers and procurement teams specifying panels for truck bodies, trailers, and scaffolding applications.
What makes sandwich panels resistant to impact damage?
Sandwich panels resist impact damage through a combination of structural separation and material cooperation. The two stiff outer skins carry tensile and compressive loads, while the lightweight core holds them apart and transfers shear forces between them. When an impact occurs, this geometry forces the energy to travel through multiple material interfaces rather than concentrating at the surface.
The result is a structure that punches well above its weight in impact resistance relative to its mass. A solid steel plate of equivalent stiffness would be far heavier. A solid polymer sheet of equivalent weight would be far weaker. The sandwich arrangement achieves stiffness and impact resistance simultaneously because the skins are positioned at maximum distance from the neutral axis, which is where bending and impact stresses are highest.
Fibre-reinforced thermoplastic skins add a further mechanism: the glass fibres within the skin laminate can absorb and redirect energy along their length before the skin fractures. This is why skin architecture, not just skin thickness, matters for impact performance.
How do thermoplastic sandwich panels compare to steel and aluminium under impact?
Thermoplastic sandwich panels absorb impact energy differently from steel and aluminium, and in many transport applications they outperform both on a weight-adjusted basis. Steel and aluminium deform plastically under impact, meaning they dent permanently. Thermoplastic composite skins can flex and recover from lower-energy impacts, and when they do fail, they tend to crack locally rather than crumple across a wide area.
For truck body builders and trailer manufacturers, this distinction has a direct commercial consequence. A steel panel that takes a forklift strike in a loading bay typically requires panel replacement or bodywork repair. A composite panel may sustain a localised skin crack that can be assessed and, in many cases, left in service or repaired without full panel replacement.
Weight is the other side of this comparison. Steel body panels add significant structural dead weight that eats into legally permitted payload capacity. Every kilogram saved in the body structure is a kilogram that can carry revenue-generating cargo. In 2026, this argument extends beyond payload to battery range: lighter body structures extend range per charge in electric trucks and vans, making weight reduction a range argument as well as a payload argument. EV fleet procurement teams now treat this as a standard specification question.
Aluminium performs better than steel on weight but still cannot match the stiffness-to-weight ratio of a well-specified glass-fibre thermoplastic sandwich panel, particularly in floor and wall panel applications where panel thickness can be used to engineer in the required bending performance without adding mass.
What role does the skin material play in impact performance?
The skin material is the primary determinant of impact resistance in a sandwich panel. The skin is the first layer to receive an impact load, and its ability to distribute that load across a wider area before it reaches the core determines whether the panel survives intact or fails locally.
Glass-fibre-reinforced thermoplastic skins perform well in impact scenarios because the fibre network spreads the load laterally while the thermoplastic matrix absorbs energy through deformation. The fibre architecture within the skin matters significantly:
- Cross-ply laminates orient fibres at 0° and 90° in alternating layers, which equalises mechanical properties in both directions and makes the panel equally resistant to impacts from any direction. This is particularly useful for wall panels that may be struck from multiple angles.
- Multi-ply unidirectional laminates (such as 4-ply skins) build up thickness in a controlled way, increasing the skin’s ability to resist penetration under concentrated loads.
Surface finish also plays a role. Anti-skid surfaces on floor panels add a textured layer that distributes point loads slightly before they reach the structural skin beneath. PET-film surfaces on wall panels provide a hard, smooth outer face that resists surface abrasion and minor impacts without compromising the underlying laminate.
Glass fibre content within the skin is another variable. Higher fibre content by volume generally improves stiffness and impact resistance, though the relationship is not linear and depends on fibre orientation and laminate quality.
Does core material affect how a sandwich panel absorbs impact?
Yes, the core material significantly affects how a sandwich panel absorbs impact, though its role is different from the skin’s. The core does not resist the initial impact directly. Instead, it controls how the skins behave under load by maintaining their separation and transferring shear forces between them. A core that fails under impact allows the skins to move independently, which collapses the panel’s structural advantage.
PP-foam cores
Oriented polypropylene foam cores are available in a range of densities, from 40 kg/m³ up to 140 kg/m³. Higher-density foam cores provide greater shear strength and resist core crushing under concentrated loads. Lower-density grades reduce panel weight but offer less resistance to localised impact. The choice of foam density is therefore a direct engineering decision that trades weight against impact tolerance, and it can be tuned to the specific demands of the application.
PP-honeycomb cores
PP-honeycomb cores at 140 kg/m³ deliver substantially higher bending and compressive performance than foam cores of similar thickness. Floor panels built with PP-honeycomb cores sustain significantly higher maximum loads in bending tests, which reflects their ability to maintain skin separation under concentrated force. For applications like truck body floors where point loads from pallets, forklifts, or cargo are common, honeycomb cores provide a meaningful performance advantage. The trade-off is that honeycomb panels are heavier than foam-core panels of equivalent thickness.
How are sandwich panels tested for impact resistance?
Sandwich panels are evaluated through a combination of standardised mechanical tests that measure the properties most relevant to real-world impact scenarios. No single test captures all impact conditions, so engineers typically review several test results together when specifying panels for demanding applications.
The most relevant tests for European applications include:
- Bending strength (ISO 14125): A three-point bending test that measures how much force a panel can sustain before failure. This is directly relevant to impact scenarios where a panel is loaded across its span, such as a floor panel struck by a dropped load.
- Tensile testing (EN ISO 527): Measures the skin’s ability to resist tensile stress, which occurs on the face opposite the impact point during bending.
- Compressive testing: Relevant for core materials, measuring resistance to crushing under concentrated loads.
For scaffolding panels, load class performance under EN 12811 provides a direct reference point for impact and distributed load tolerance in working conditions. A panel that achieves EN 12811 load class 4 with no support underneath has demonstrated a specific, verifiable level of structural performance under load.
It is worth noting that standardised test results are geometry-dependent. Bending strength values in MPa will differ between a 15 mm and a 30 mm panel tested on the same span, even if the absolute maximum load the thicker panel sustains is higher. Reading test data correctly requires understanding the test geometry, not just the headline figure.
When does a sandwich panel fail under impact, and what does failure look like?
A sandwich panel fails under impact when the energy of the strike exceeds the capacity of either the skin or the core to absorb and distribute it. The failure mode depends on which component reaches its limit first, and the two failure types look and behave very differently.
Skin failure typically appears as a crack or fracture in the outer laminate at the point of impact. In glass-fibre thermoplastic skins, this often takes the form of a localised crack rather than a large-area fracture, because the fibre network arrests crack propagation. The panel may retain significant structural capacity even after a skin crack, particularly if the core remains intact and the opposite skin is undamaged.
Core failure is more serious. If the core crushes or shears under impact, the two skins lose their structural separation and the panel’s bending stiffness collapses. Core failure is not always visible from the surface, which is why panels that have sustained significant impact loads should be assessed structurally, not just visually inspected.
Delamination is a third failure mode, where the bond between skin and core breaks down. This can occur at impact points or, in lower-quality panels, progressively over time as repeated loading cycles stress the adhesive interface. Thermoplastic sandwich panels that use a fully fused thermoplastic bond between skin and core are less susceptible to delamination than panels where the skin is adhesively bonded to a dissimilar core material.
In practice, well-specified panels in transport applications are designed with a margin above the expected service loads, so outright failure under normal operating conditions is uncommon. The more relevant question for most OEMs is how the panel performs after repeated lower-energy impacts over its service life, and whether it maintains its structural properties across a 12-year or longer vehicle lifespan.
How Compoform Helps with Sandwich Panel Impact Performance
We engineer thermoplastic sandwich panels specifically for the impact conditions your application creates, not to a generic specification. For truck body builders, trailer manufacturers, and scaffolding companies, that means reviewing your load scenarios before recommending a panel configuration, rather than offering a catalogue product and leaving the integration risk with you.
Here is what that looks like in practice:
- Core selection matched to your load profile. We offer PP-foam cores across six density grades (40 to 140 kg/m³) and PP-honeycomb cores for high-load floor applications. We help you identify which core delivers the impact tolerance you need at the lowest panel weight.
- Skin architecture optimised for your impact direction. Cross-ply laminates for wall panels that need equal resistance in both orientations; multi-ply skins for floor panels where concentrated point loads dominate.
- Panels produced to your exact dimensions. Maximum panel size is 13,500 mm × 2,950 mm, manufactured in the Netherlands. No off-the-shelf compromise, no minimum order constraint that forces you to cut down oversized stock.
- Verified performance data. Our floor panels are tested to ISO 14125 and our scaffolding panels are qualified to EN 12811 load class 4. We share test data transparently so your engineering team can validate the specification before committing to production.
- Long service life that reduces total cost. Thermoplastic composite floors last three to four times longer than plywood in heavy transport applications. Over a 15-year vehicle life, that eliminates two to three replacement cycles. When you factor in panel cost, installation labour, and vehicle downtime, the composite is cheaper per year of service even at a higher unit price.
We work as an application partner, not a panel supplier. That means we review your design, flag integration issues before they reach production, and stay engaged through the build process. If you are specifying panels for a truck body floor, trailer wall, or scaffolding board and want to work through the impact requirements for your specific application, contact our engineering team for panel specifications to start the conversation.