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Composite core

There are few cabin spaces where composite structures have yet to find their place, from galleys and other thermally challenging environments, to pearlescent or metallic-effect seat components and the largest, most complex ceiling panels, as Paul E Eden reveals

Composites are among the most widespread materials in aircraft cabins today. The possibilities they enable have changed dramatically over a relatively short timescale, especially as the concept of passenger experience has evolved and the industry came to recognise aesthetics as a crucial part of the customer experience.


Dan Freeman, Boeing’s Director – Payloads Engineering, says: “Composites have been widely used in aircraft interiors since the late 1970s, with the introduction of the 757 and 767, along with design upgrades on the 747. Early composite panels employed a Nomex honeycomb core between either fibreglass or carbon sheets pre-impregnated with resin. They were either laid up on a tool and oven cured, or inserted into a large press with a contoured mould die to be ‘crushed’ and cured in one step.


“Over time this basic honeycomb core/covering sheets construction has changed little, but fabrication processes, material chemistry and post-forming panel operations have evolved significantly. Flat panels used to be produced one at a time using a vacuum bag and oven, for example, but now many panels are fabricated at once in multi-opening presses.


“Resin chemistry has evolved to provide higher strength, improved curing properties and better fire resistance, while panel joining techniques have moved away from installing inserts into panels to attach brackets with screws, to lower weight and cost solutions where panels are joined using a tab-and-slot method.”


Freeman describes the classic composite panel construction that remains as relevant today as in the 1970s, but materials used in other cabin components, especially complex items, including seat parts, employ a very different manufacturing process. Headquartered in Newcomerstown, OH, Boltaron specialises in producing PVC, PVC-alloy and CPVC (chlorinated polyvinyl chloride) sheet materials for a wide range of applications, including aerospace. 


Adam Mellen, Chief Sales Officer, explains: “Our composites are created using press lamination, which uses pressure and heat to bond the layers together. The honeycomb core-type is typically used to make furniture or as more of a structural composite. Our composite material is not structural, but uses the construction of multiple substrates to create one sheet or finished formed component.”


Boltaron and parent SIMONA are leaders in PVC and CPVC for industrial applications, but Boltaron’s PVC- alloy is formulated for aircraft interiors, specifically to meet the FAR 25.853(a) and (d) regulations for smoke and heat release. The product is available in an array of finishes. “The metallics and pearlescent effects are integral to the product, not applied post-production,” Mellen says. “Our unique technology permanently integrates a durable metallic cap layer and a colour-matched substrate for a deeper, richer appearance than a metallic-coloured monolithic sheet. This gives greater design freedom and a longer service life to the component with the metallic effect.”


Through thermoforming, these materials are used to create complex, aesthetically pleasing components with no requirement for painting or external finish; but how well do they fare under the rigours of day-to-day airline use?


“We use a proprietary scratch-resistant formulation unique to our material, while impact resistance is one of our founding core principles of performance. The material is engineered to stand up to the impact of suitcases, galley carts and even in-process seat fabrication, where the sheets are moved around and manipulated in production.”


And if damage should occur? “Depending on the scratch or damage, colour and textures, there are different methods of repairing the sheet. Our in-house diagnostic team is expert at handling each need as it comes up.”


All over the plane

SEKISUI SPI’s KYDEX thermoplastics range also has a broad portfolio of applications within the cabin.

Ben Smalley, Aviation Market Business Manager, comments: “Although KYDEX is known for passenger-facing applications like seating and monuments, it’s also commonly used in less aesthetic but equally demanding applications, including galleys and lavatories, as well as on flight deck seating and components.


 “Our KYDEX 6565, 5555 and 4545 range meet or exceed the FAR 25.853(d) requirements for flame spread, smoke development and heat release. They’re used for housings and covers throughout the cabin; they’re invisible to the passenger, but critical for passenger safety, aircraft weight savings and the durability of the interior.


 “Products like KYDEX 7200ST and FST reside in the ‘hidden part’ of our portfolio. They meet the highest standards of aviation interior requirements, but don’t require the aesthetic demands of cabin interiors. They’re more commonly used in galleys and flight deck applications, or where higher ‘in use’ temperatures are required.”


KYDEX is available in more than 4,000 bespoke colours and, like Boltaron, does not require further protection in use. In particular, Smalley notes its resistance to damage through repeated cleaning. “Our materials are tested to ensure commercial aviation interior cleaners don’t affect their colour or physical properties. This can be challenging for some thermoplastics. Polycarbonate products are prone to cracking or hazing after repeated cleaning, and some materials have a tendency to ‘turn brown’ after repeated cleaning unless an additional coating is applied. These cleaning agents have no effect on KYDEX and no ‘special coating’ is required.” >>


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