How do sandwich panels meet aerospace weight and strength requirements?

Compoform · 18 Sep 2026

Sandwich panels meet aerospace weight and strength requirements by combining two thin, high-strength face skins bonded to a lightweight core. This structure places stiff material where bending stress is highest — at the outer faces — while the core resists shear and maintains separation between the skins. The result is a panel that delivers structural performance comparable to solid metal at a fraction of the weight. The sections below address the most common engineering questions about sandwich panels in demanding structural applications.

Note: 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 materials are used in aerospace sandwich panels?

Aerospace sandwich panels typically use carbon fibre or glass fibre reinforced polymer (FRP) face skins bonded to a lightweight core, most commonly aluminium honeycomb or Nomex aramid honeycomb. The face skins carry tensile and compressive loads, while the core maintains the separation between them and transfers shear forces. Material selection depends on the load case, temperature range, and weight budget for each specific application.

Face skin materials in aerospace applications generally fall into two categories:

Carbon fibre reinforced polymer (CFRP): Used where maximum stiffness-to-weight ratio is needed. Carbon fibre skins offer a high tensile modulus and are common in primary structural panels on commercial and military aircraft.
Glass fibre reinforced polymer (GFRP): Lower cost than carbon, with good impact resistance and electrical transparency. Often used in radomes, interior panels, and secondary structures.

Core materials vary by application. Aluminium honeycomb is widely used for its compressive strength and thermal conductivity. Nomex honeycomb, made from aramid paper, offers better fire resistance and is common in cabin interiors. Foam cores, including polymethacrylimide (PMI) and polyetherimide (PEI) foams, appear in applications where complex curvature or moisture resistance is a priority.

Resin systems in aerospace are predominantly epoxy-based thermosets, processed under elevated temperature and pressure in an autoclave. Thermoplastic matrix systems, including PEEK and PPS, are gaining ground in aerospace for their recyclability and resistance to impact damage.

How does a sandwich panel achieve high strength at low weight?

A sandwich panel achieves high strength at low weight through structural geometry rather than material mass. By separating two stiff face skins with a low-density core, the panel increases its second moment of area — the geometric property that governs resistance to bending — without adding proportional weight. This is the same principle that makes an I-beam stiffer than a solid rectangular bar of equal mass.

When a sandwich panel bends under load, the face skins experience tension on one side and compression on the other. Placing high-modulus material at the outermost surfaces maximises the panel’s resistance to these stresses. The core, which sits at the neutral axis where bending stress is lowest, does not need to be strong in tension or compression — it needs to resist shear and prevent the skins from buckling inward or delaminating.

This division of labour is what makes sandwich construction so efficient. A panel can be made thicker — increasing bending stiffness significantly — simply by using a thicker core, without adding much weight. Doubling the core thickness roughly quadruples the panel’s flexural stiffness while adding only the weight of the additional core material, which is typically very low in density.

The bond between skin and core is equally important. If the adhesive or lamination interface fails, the skins lose their separation and the panel collapses to the strength of the skins alone. In well-designed sandwich panels, the interface is engineered to transfer shear loads continuously across the full panel area.

What are the key aerospace standards sandwich panels must meet?

Aerospace sandwich panels must meet certification requirements set by airworthiness authorities, primarily the European Union Aviation Safety Agency (EASA) and the US Federal Aviation Administration (FAA). These requirements cover structural performance, fire behaviour, and material qualification. The specific standards depend on whether the panel is used in a primary structure, secondary structure, or interior application.

Key areas of compliance include:

Structural qualification: Panels used in primary structures must demonstrate strength and stiffness under defined load cases, including static, fatigue, and damage tolerance testing. Material allowables are established through statistically significant test programmes.
Fire, smoke, and toxicity (FST): Interior panels must meet FAR 25.853 (US) or CS-25 (European) requirements for flame spread, smoke density, and toxic gas emission. This is particularly demanding for cabin floor panels, overhead bins, and wall liners.
Environmental resistance: Panels must maintain structural integrity after exposure to humidity, temperature cycling, and fluids such as hydraulic oil and cleaning agents.
Damage tolerance: Aerospace panels must retain a defined percentage of their original strength after impact damage, including barely visible impact damage (BVID) that may not be detectable during routine inspection.

Material and process qualification follows guidelines such as ASTM standards for mechanical testing and SACMA recommended methods for composite-specific properties. European programmes increasingly reference EN ISO standards for tensile and flexural testing. Any change to material supplier, process parameters, or panel geometry typically triggers a re-qualification programme.

How do sandwich panels compare to aluminium sheets in aerospace?

Sandwich panels outperform solid aluminium sheet in bending stiffness and weight efficiency for most aerospace panel applications. A composite sandwich panel can achieve equivalent or greater flexural stiffness at significantly lower areal weight than an aluminium sheet of comparable thickness. The trade-off is that aluminium sheet is simpler to repair, more tolerant of point loads, and easier to join using conventional fasteners.

The comparison depends heavily on the load case. For large, flat panels loaded primarily in bending — such as floor panels, fairings, and access doors — sandwich construction is almost always lighter than solid aluminium for the same stiffness. For fittings, brackets, and areas with concentrated fastener loads, solid aluminium or machined metal remains the preferred choice because sandwich panels are vulnerable to localised crushing at fastener locations without reinforcement inserts.

From a manufacturing standpoint, aluminium sheet is faster to cut, form, and join using established metalworking processes. Sandwich panels require more controlled manufacturing conditions, careful handling to avoid skin damage, and specialist joining techniques. However, the weight savings translate directly into fuel savings over the aircraft’s service life, which is why the industry has progressively replaced aluminium sheet with sandwich panels in secondary structures and interiors over recent decades.

Repairability is a genuine limitation of sandwich panels in service. Skin delamination, core crushing, and moisture ingress require specialist repair procedures. Aluminium sheet can be patched or replaced more quickly by maintenance crews with standard tooling.

What causes sandwich panel failure in aerospace applications?

Sandwich panel failure in aerospace applications occurs through several distinct mechanisms, each driven by a different combination of load type and panel geometry. The most common failure modes are face skin fracture, core shear failure, skin-to-core delamination, and local skin buckling. Understanding which mode governs a given design is necessary to size the panel correctly and avoid unexpected failure.

Face skin fracture: Occurs when the tensile or compressive stress in the skin exceeds the material’s strength. This is the intended failure mode in a well-designed panel — the skins should be the limiting element, not the core or interface.
Core shear failure: The core fails in shear when the panel spans a long distance relative to its thickness, or when the core density is insufficient for the applied load. This is a sudden failure mode and must be avoided in primary structures.
Skin-to-core delamination: The bond between skin and core fails, allowing the skins to slide relative to the core. This can result from manufacturing defects, impact damage, or moisture degradation of the adhesive interface over time.
Local skin buckling (wrinkling): The compressed skin buckles locally into the core before the skin material reaches its strength limit. This occurs when the core is too soft to provide adequate lateral support to the skin in compression.
Moisture ingress: Water entering through damaged skins or poorly sealed edges degrades the core and adhesive, reducing structural performance progressively. In honeycomb cores, trapped moisture can freeze at altitude and cause further damage.

Impact damage is a particular concern because it can cause internal delamination or core crushing that is not visible on the surface. Non-destructive inspection methods, including ultrasonic C-scan and thermography, are used in aerospace maintenance programmes to detect this type of hidden damage.

When should engineers choose thermoplastic over thermoset sandwich panels?

Engineers should choose thermoplastic sandwich panels when recyclability, impact resistance, and production speed are priorities. Thermoplastic matrix systems can be remelted and reformed, making them compatible with end-of-life recycling requirements. They also absorb impact energy more effectively than brittle thermoset systems and can be processed using faster, press-based manufacturing methods that suit high-volume production runs.

Thermoset panels, processed in an autoclave with epoxy resin systems, remain the standard for primary aerospace structures where maximum stiffness, elevated temperature resistance, and proven certification data are needed. Thermosets cure irreversibly, which limits repairability but also produces a dimensionally stable, high-performance laminate that has decades of in-service data behind it.

The decision between thermoplastic and thermoset comes down to several practical factors:

Temperature requirements: Thermosets generally outperform thermoplastics at elevated operating temperatures. High-performance thermoplastics such as PEEK close this gap but at significantly higher material cost.
Production volume and cycle time: Thermoplastic panels can be consolidated in minutes using heated press processes. Autoclave-cured thermoset panels require hours per cycle, making thermoplastics more suitable for volume production.
Recyclability and regulatory compliance: European sustainability regulations, including the EU ELV Directive and CSRD reporting requirements, are pushing OEMs toward thermoplastic systems that can be recycled at end of life. Thermoset panels cannot be remelted and are more difficult to recycle.
Impact performance: Thermoplastic skins typically absorb more energy before fracture than thermoset equivalents, which is relevant for panels exposed to tool drops, ground handling, and debris impact.

In commercial vehicle and ground transport applications — where the regulatory pressure on recyclability is already significant and production volumes are higher than in aerospace — thermoplastic sandwich panels are increasingly the default choice rather than the alternative.

How Compoform Supports Your Sandwich Panel Specification

We design and manufacture fully custom thermoplastic sandwich panels using PP honeycomb and PET foam cores, with glass fibre reinforced thermoplastic skins in cross-ply and multi-ply configurations. Our panels are produced on a 72-metre double belt press line at our facilities in the Netherlands, with panel dimensions up to 13,500 mm x 2,950 mm x 150 mm available to order.

For engineers and procurement teams specifying panels for commercial vehicle bodies, trailer floors, and scaffolding applications, we offer the following as standard:

Custom panel configuration: You specify core thickness, core density, skin ply count, fibre orientation, and surface finish. We engineer the panel to your load case, not to a catalogue.
Tested performance data: All panel configurations are tested to ISO 14125 for flexural performance and EN ISO standards for tensile properties. We provide technical data sheets with actual test results, not estimated values.
Application engineering support: Before production, we review your design, assess the load requirements, and flag any configuration issues that could affect performance or assembly. This step eliminates costly surprises during integration.
Edge sealing and surface options: Anti-skid surfaces for floor panels, PET film finishes for wall cladding, and edge sealing to protect the core from moisture and UV exposure in service.

A 30 mm PP sandwich floor panel from our range is self-supporting with no aluminium subframe required, which removes a production step and reduces cost for truck body builders. Over a 15-year vehicle life, eliminating two to three plywood replacement cycles — each requiring panel cost, installation labour, and vehicle downtime — makes the composite the lower-cost option per year of service, even at a higher unit price.

If you are reviewing a panel specification for a commercial vehicle, trailer, or scaffolding application, speak with our engineering team about your load requirements and assembly constraints. We will review the configuration with you before anything goes to production.